System.IO.File Class

public sealed class File

Base Types

Object
File

Assembly

mscorlib

Library

BCL

Summary

Provides information and performs operations on files .

Description

Implementations of this class are required to preserve the case of path strings. Implementations are required to be case sensitive if and only if the platform is case-sensitive.
The following table describes the enumerations that are used to customize the behavior of various File methods.

Enumeration Description

FileAccess Specifies read and write access to a file.

FileShare Specifies the level of access permitted for a file that is already in use.

FileMode Specifies whether the contents of an existing file are preserved or overwritten, and whether requests to create an existing file cause an exception.

Enumeration	Description
FileAccess	Specifies read and write access to a file.
FileShare	Specifies the level of access permitted for a file that is already in use.
FileMode	Specifies whether the contents of an existing file are preserved or overwritten, and whether requests to create an existing file cause an exception.

Members

File Methods
File.AppendText Method
File.Copy(System.String, System.String) Method
File.Copy(System.String, System.String, bool) Method
File.Create(System.String) Method
File.Create(System.String, int) Method
File.CreateText Method
File.Delete Method
File.Exists Method
File.GetCreationTime Method
File.GetLastAccessTime Method
File.GetLastWriteTime Method
File.Move Method
File.Open(System.String, System.IO.FileMode, System.IO.FileAccess, System.IO.FileShare) Method
File.Open(System.String, System.IO.FileMode, System.IO.FileAccess) Method
File.Open(System.String, System.IO.FileMode) Method
File.OpenRead Method
File.OpenText Method
File.OpenWrite Method
File.SetCreationTime Method
File.SetLastAccessTime Method
File.SetLastWriteTime Method

File.AppendText Method

public static StreamWriter AppendText(string path);

Summary

Appends UTF-8 encoded text to an existing file.

Parameters

path

A String containing the name of the file to append to.

Return Value

A StreamWriter that appends UTF-8 encoded text to the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

DirectoryNotFoundException The directory information specified in path was not found.

System.IO.Exception A general I/O exception occurred, such as trying to access a CD-ROM drive whose tray is open.

System.IO.NotSupportedException path is in an implementation-specific invalid format.

PathTooLongException The length of path or the absolute path information for path exceeds the implementation-specific maximum length.

UnauthorizedAccessException Access is denied. The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
DirectoryNotFoundException	The directory information specified in path was not found.
System.IO.Exception	A general I/O exception occurred, such as trying to access a CD-ROM drive whose tray is open.
System.IO.NotSupportedException	path is in an implementation-specific invalid format.
PathTooLongException	The length of path or the absolute path information for path exceeds the implementation-specific maximum length.
UnauthorizedAccessException	Access is denied. The caller does not have the required permission.

Description

This method is equivalent to StreamWriter (path, true ). If the file specified by path does not exist, it is created. If the file does exist, writes to the StreamWriter append text to the file. Additional threads are permitted to read the file while it is open.
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Copy(System.String, System.String) Method

public static void Copy(string sourceFileName, string destFileName);

Summary

Copies the specified file to a new location.

Parameters

sourceFileName

A String containing the name of the file to copy.

destFileName

A String containing the name of the destination file. Cannot specify a directory or an existing file.

Exceptions

Exception Type Condition

ArgumentException sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
-or-
sourceFileName or destFileName specifies a directory.

ArgumentNullException sourceFileName or destFileName is null .

DirectoryNotFoundException Directory information in sourceFileName or destFileName was not found.

FileNotFoundException sourceFileName was not found.

IOException destFileName exists.
-or-
An I/O error occurred.

PathTooLongException The length or the absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters. -or- sourceFileName or destFileName specifies a directory.
ArgumentNullException	sourceFileName or destFileName is `null` .
DirectoryNotFoundException	Directory information in sourceFileName or destFileName was not found.
FileNotFoundException	sourceFileName was not found.
IOException	destFileName exists. -or- An I/O error occurred.
PathTooLongException	The length or the absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to System.IO.File.Copy(System.String,System.String) (sourceFileName, destFileName, false ).
The sourceFileName and destFileName arguments are permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Copy(System.String, System.String, bool) Method

public static void Copy(string sourceFileName, string destFileName, bool overwrite);

Summary

Copies the specified file to a new location.

Parameters

sourceFileName

A String containing the name of the file to copy.

destFileName

A String containing the name of the destination file. Cannot specify the name of a directory.

overwrite

A Boolean value. Specify true if the destination file can be overwritten; otherwise false .

Exceptions

Exception Type Condition

ArgumentException sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more invalid characters.
-or-
sourceFileName or destFileName specifies a directory.

ArgumentNullException sourceFileName or destFileName is null .

DirectoryNotFoundException Directory information in destFileName or sourceFileName was not found.

FileNotFoundException sourceFileName was not found.

IOException destFileName is read-only (write-protected), or destFileName exists and overwrite is false .
-or-
An I/O error occurred.

PathTooLongException The length or the absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more invalid characters. -or- sourceFileName or destFileName specifies a directory.
ArgumentNullException	sourceFileName or destFileName is `null` .
DirectoryNotFoundException	Directory information in destFileName or sourceFileName was not found.
FileNotFoundException	sourceFileName was not found.
IOException	destFileName is read-only (write-protected), or destFileName exists and overwrite is `false` . -or- An I/O error occurred.
PathTooLongException	The length or the absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The sourceFileName and destFileName arguments are permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Create(System.String) Method

public static FileStream Create(string path);

Summary

Creates or overwrites the specified file.

Parameters

path

A String containing the name of the file.

Return Value

A FileStream that provides read/write access to the specified file.

Exceptions

Exception Type Condition

ArgumentNullException path is null .

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

UnauthorizedAccessException path specified a file that is read-only (write-protected).

DirectoryNotFoundException The directory information specified in path was not found.

IOException An I/O error occurred while creating the file.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentNullException	path is `null` .
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
UnauthorizedAccessException	path specified a file that is read-only (write-protected).
DirectoryNotFoundException	The directory information specified in path was not found.
IOException	An I/O error occurred while creating the file.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

If the specified file does not exist, it is created; if it does exist and it is not read-only, the contents are overwritten.
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Create(System.String, int) Method

public static FileStream Create(string path, int bufferSize);

Summary

Creates or overwrites the specified file.

Parameters

path

A String containing the name of the file.

bufferSize

A Int32 containing the number of bytes buffered for reads and writes to the file.

Return Value

A FileStream that provides read/write access to the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

UnauthorizedAccessException path specified a file that is read-only (write-protected).

DirectoryNotFoundException The directory information specified in path was not found.

IOException An I/O error occurred while creating the file.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
UnauthorizedAccessException	path specified a file that is read-only (write-protected).
DirectoryNotFoundException	The directory information specified in path was not found.
IOException	An I/O error occurred while creating the file.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to FileStream (path, System.IO.FileMode.Create, System.IO.FileAccess.ReadWrite, System.IO.FileShare.None , bufferSize).
If the specified file does not exist, it is created; if it does exist and it is not read-only, the contents are overwritten.
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.CreateText Method

public static StreamWriter CreateText(string path);

Summary

Creates or opens a file for writing UTF-8 encoded text.

Parameters

path

The file to be opened for writing.

Return Value

A StreamWriter that writes to the specified file using UTF-8 encoding.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

DirectoryNotFoundException The directory information specified in path was not found.

System.IO.Exception A general I/O exception occurred, such as trying to access a CD-ROM drive whose tray is open.

System.IO.NotSupportedException path is in an implementation-specific invalid format.

PathTooLongException The length of path or the absolute path information for path exceeds the implementation-specific maximum length.

UnauthorizedAccessException Access is denied. The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
DirectoryNotFoundException	The directory information specified in path was not found.
System.IO.Exception	A general I/O exception occurred, such as trying to access a CD-ROM drive whose tray is open.
System.IO.NotSupportedException	path is in an implementation-specific invalid format.
PathTooLongException	The length of path or the absolute path information for path exceeds the implementation-specific maximum length.
UnauthorizedAccessException	Access is denied. The caller does not have the required permission.

Description

This method is equivalent to StreamWriter (path, false ). If the file specified by path does not exist, it is created. If the file does exist, its contents are overwritten. Additional threads are permitted to read the file while it is open.
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.

File.Delete Method

public static void Delete(string path);

Summary

Deletes the specified file.

Parameters

path

A String containing the name of the file to be deleted.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

UnauthorizedAccessException path identifies a directory.
-or-
path specifies a file that is read-only.

DirectoryNotFoundException The directory information specified in path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
UnauthorizedAccessException	path identifies a directory. -or- path specifies a file that is read-only.
DirectoryNotFoundException	The directory information specified in path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

[Note: Some implementations might throw IOException to cover such implementation-specific conditions as "file in use".]

File.Exists Method

public static bool Exists(string path);

Summary

Returns a Boolean indicating whether the specified file exists.

Parameters

path

A String containing the name of the file to check.

Return Value

true if the caller has the required permissions and path contains the name of an existing file; otherwise, false . If path is null or a zero-length string, returns false .

Description

If the caller does not have sufficient permissions to read the specified file, no exception is thrown and the method returns false regardless of the existence of path.
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.GetCreationTime Method

public static DateTime GetCreationTime(string path);

Summary

Returns the creation date and time of the specified file or directory.

Parameters

path

A String containing the name of the file or directory for which to obtain creation date and time information.

Return Value

A DateTime structure set to the creation date and time for the specified file or directory. This value is expressed in local time.
Platforms that do not support this feature return System.DateTime.MinValue.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

IOException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
IOException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.GetLastAccessTime Method

public static DateTime GetLastAccessTime(string path);

Summary

Returns the date and time the specified file or directory was last accessed.

Parameters

path

A String containing the name of the file or directory for which to obtain access date and time information.

Return Value

A DateTime structure set to the date and time the specified file or directory was last accessed. This value is expressed in local time.
Platforms that do not support this feature return System.DateTime.MinValue.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

IOException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
IOException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.GetLastWriteTime Method

public static DateTime GetLastWriteTime(string path);

Summary

Returns the date and time the specified file or directory was last written to.

Parameters

path

A String containing the name of the file for which to obtain write date and time information.

Return Value

A DateTime structure set to the date and time the specified file or directory was last written to. This value is expressed in local time.
Platforms that do not support this feature return System.DateTime.MinValue.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

IOException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
IOException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Move Method

public static void Move(string sourceFileName, string destFileName);

Summary

Moves the specified file to a new location.

Parameters

sourceFileName

A String containing the name of the file to move.

destFileName

A String containing the name of the new location for the file.

Exceptions

Exception Type Condition

ArgumentException sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException sourceFileName or destFileName is null .

DirectoryNotFoundException The directory information in sourceFileName or destFileName was not found.

FileNotFoundException sourceFileName was not found or specifies a directory.

IOException destFileName already exists or is a directory.

PathTooLongException The length or absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	sourceFileName or destFileName is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	sourceFileName or destFileName is `null` .
DirectoryNotFoundException	The directory information in sourceFileName or destFileName was not found.
FileNotFoundException	sourceFileName was not found or specifies a directory.
IOException	destFileName already exists or is a directory.
PathTooLongException	The length or absolute path information for sourceFileName or destFileName exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method does not throw an exception if the source and destination are the same.
The sourceFileName and destFileName arguments are permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Open(System.String, System.IO.FileMode, System.IO.FileAccess, System.IO.FileShare) Method

public static FileStream Open(string path, FileMode mode, FileAccess access, FileShare share);

Summary

Opens a FileStream on the specified file.

Parameters

path

A String containing the name of the file to open.

mode

A FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.

access

A FileAccess value that specifies the operations that can be performed on the file.

share

A FileShare value specifying the type of access other threads have to the file.

Return Value

A FileStream that provides access to the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
-or-
access specified Read and mode specified Create , CreateNew , Truncate or Append .

ArgumentNullException path is null .

ArgumentOutOfRangeException mode, access, or share specified an invalid value.

UnauthorizedAccessException path specified a read-only file and access is not Read , or path specified a directory.

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException path was not found.

IOException An I/O error occurred while opening the file.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters. -or- access specified `Read` and mode specified `Create` , `CreateNew` , `Truncate` or `Append` .
ArgumentNullException	path is `null` .
ArgumentOutOfRangeException	mode, access, or share specified an invalid value.
UnauthorizedAccessException	path specified a read-only file and access is not `Read` , or path specified a directory.
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	path was not found.
IOException	An I/O error occurred while opening the file.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to FileStream (path, mode, access, share).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Open(System.String, System.IO.FileMode, System.IO.FileAccess) Method

public static FileStream Open(string path, FileMode mode, FileAccess access);

Summary

Opens a FileStream on the specified file.

Parameters

path

A String containing the name of the file to open.

mode

A FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.

access

A FileAccess value that specifies the operations that can be performed on the file.

Return Value

A FileStream that provides access to the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
-or-
access specified Read and mode specified Create , CreateNew , Truncate or Append .

ArgumentNullException path is null .

ArgumentOutOfRangeException mode or access specified an invalid value.

UnauthorizedAccessException path specified a read-only file and access is not Read , or path specified a directory.

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException mode is System.IO.FileMode.Truncate or System.IO.FileMode.Open, but the specified file was not found. If a different mode is specified and the file was not found, a new one is created.

IOException An I/O error occurred, such as specifying System.IO.FileMode.CreateNew when the file specified by path already exists.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters. -or- access specified `Read` and mode specified `Create` , `CreateNew` , `Truncate` or `Append` .
ArgumentNullException	path is `null` .
ArgumentOutOfRangeException	mode or access specified an invalid value.
UnauthorizedAccessException	path specified a read-only file and access is not `Read` , or path specified a directory.
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	mode is System.IO.FileMode.Truncate or System.IO.FileMode.Open, but the specified file was not found. If a different mode is specified and the file was not found, a new one is created.
IOException	An I/O error occurred, such as specifying System.IO.FileMode.CreateNew when the file specified by path already exists.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.

Description

This method is equivalent to FileStream (path, mode, access, System.IO.FileShare.None ).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.Open(System.String, System.IO.FileMode) Method

public static FileStream Open(string path, FileMode mode);

Summary

Opens a FileStream on the specified file with read/write access.

Parameters

path

A String containing the name of the file to open.

mode

A FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.

Return Value

A FileStream that provides read/write access to the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

ArgumentOutOfRangeException mode specified an invalid value.

UnauthorizedAccessException path specified a read-only file (this method attempts to open the file with read/write access).
-or-
This operation is not supported on the current platform.
-or-
path specified a directory.

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException path was not found.

IOException An I/O error occurred while opening the file.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
ArgumentOutOfRangeException	mode specified an invalid value.
UnauthorizedAccessException	path specified a read-only file (this method attempts to open the file with read/write access). -or- This operation is not supported on the current platform. -or- path specified a directory.
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	path was not found.
IOException	An I/O error occurred while opening the file.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to FileStream (path, mode, System.IO.FileAccess.ReadWrite, System.IO.FileShare.None ).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.OpenRead Method

public static FileStream OpenRead(string path);

Summary

Opens an existing file for reading.

Parameters

path

A String containing the name of the file to be opened for reading.

Return Value

A read-only FileStream containing the contents of the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

UnauthorizedAccessException path specified a directory.

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
UnauthorizedAccessException	path specified a directory.
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to FileStream (path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read ).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.OpenText Method

public static StreamReader OpenText(string path);

Summary

Opens an existing UTF-8 encoded text file for reading.

Parameters

path

A String containing the name of the file to be opened for reading.

Return Value

A StreamReader containing the contents of the specified file.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to StreamReader (path).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.OpenWrite Method

public static FileStream OpenWrite(string path);

Summary

Opens an existing file for writing.

Parameters

path

A String containing the name of the file to be opened for writing.

Return Value

A writable FileStream that writes to the file specified by path.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

UnauthorizedAccessException path specified a read-only file or a directory.

DirectoryNotFoundException The directory information specified in path was not found.

FileNotFoundException path was not found.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
UnauthorizedAccessException	path specified a read-only file or a directory.
DirectoryNotFoundException	The directory information specified in path was not found.
FileNotFoundException	path was not found.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

This method is equivalent to FileStream (path, System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.Write, System.IO.FileShare.None ).
The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

File.SetCreationTime Method

public static void SetCreationTime(string path, DateTime creationTime);

Summary

Sets the creation date and time for the specified file.

Parameters

path

A String containing the name of the file for which to set the creation date and time information.

creationTime

A DateTime containing the value to set for the creation date and time of path. This value is expressed in local time.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentOutOfRangeException creationTime specifies a value outside the range of date/times permitted for this operation.

ArgumentNullException path is null .

FileNotFoundException path was not found.

IOException An I/O error occurred while performing the operation.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentOutOfRangeException	creationTime specifies a value outside the range of date/times permitted for this operation.
ArgumentNullException	path is `null` .
FileNotFoundException	path was not found.
IOException	An I/O error occurred while performing the operation.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

File.SetLastAccessTime Method

public static void SetLastAccessTime(string path, DateTime lastAccessTime);

Summary

Sets the date and time the specified file was last accessed.

Parameters

path

A String containing the name of the file for which to set the access date and time information.

lastAccessTime

A DateTime containing the value to set for the access date and time of path. This value is expressed in local time.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

ArgumentOutOfRangeException lastAccessTime specifies a value outside the range of date/times permitted for this operation.

FileNotFoundException path was not found.

IOException An I/O error occurred while performing the operation.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
ArgumentOutOfRangeException	lastAccessTime specifies a value outside the range of date/times permitted for this operation.
FileNotFoundException	path was not found.
IOException	An I/O error occurred while performing the operation.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

File.SetLastWriteTime Method

public static void SetLastWriteTime(string path, DateTime lastWriteTime);

Summary

Sets the date and time a file was last written to.

Parameters

path

A String containing the name of the file for which to set the date and time information.

lastWriteTime

A DateTime containing the value to set for the last write date and time of path. This value is expressed in local time.

Exceptions

Exception Type Condition

ArgumentException path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.

ArgumentNullException path is null .

ArgumentOutOfRangeException lastWriteTime specifies a value outside the range of date/times permitted for this operation.

FileNotFoundException path was not found.

IOException An I/O error occurred while performing the operation.

PathTooLongException The length of path or the absolute path information for path exceeds the system-defined maximum length.

UnauthorizedAccessException The caller does not have the required permission.

Exception Type	Condition
ArgumentException	path is a zero-length string, contains only white space, or contains one or more implementation-specific invalid characters.
ArgumentNullException	path is `null` .
ArgumentOutOfRangeException	lastWriteTime specifies a value outside the range of date/times permitted for this operation.
FileNotFoundException	path was not found.
IOException	An I/O error occurred while performing the operation.
PathTooLongException	The length of path or the absolute path information for path exceeds the system-defined maximum length.
UnauthorizedAccessException	The caller does not have the required permission.

Description

The path argument is permitted to specify relative or absolute path information. Relative path information is interpreted as relative to the current working directory. [Note: To obtain the current working directory, see System.IO.Directory.GetCurrentDirectory.]

On platforms that do not support this feature, this method has no effect. If this feature is supported, the range of dates that is valid for this operation is implementation-specific.

System.IO.File Class

Base Types

Assembly

Library

Summary

Description

See Also

Members

File.AppendText Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.Copy(System.String, System.String) Method

Summary

Parameters

Exceptions

Description

See Also

File.Copy(System.String, System.String, bool) Method

Summary

Parameters

Exceptions

Description

See Also

File.Create(System.String) Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.Create(System.String, int) Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.CreateText Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.Delete Method

Summary

Parameters

Exceptions

Description

See Also

File.Exists Method

Summary

Parameters

Return Value

Description

See Also

File.GetCreationTime Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.GetLastAccessTime Method

Summary

Parameters

Return Value

Exceptions

Description

See Also

File.GetLastWriteTime Method

Summary

Parameters

Return Value

Exceptions

Description