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MemoryMappedFile.CreateFromFile Method (String, FileMode)

Creates a memory-mapped file that has the specified access mode from a file on disk.

Namespace:  System.IO.MemoryMappedFiles
Assembly:  System.Core (in System.Core.dll)

public static MemoryMappedFile CreateFromFile(
	string path,
	FileMode mode


Type: System.String
The path to file to map.
Type: System.IO.FileMode
Access mode; must be Open.

Return Value

Type: System.IO.MemoryMappedFiles.MemoryMappedFile
A memory-mapped file that has the specified access mode.


path is an empty string, contains only white space, or has one or more invalid characters, as defined by the Path.GetInvalidFileNameChars method.


path refers to an invalid device.


mapName is an empty string. (A null reference is valid.)


mode is Append.


path is null.


mode is Create, CreateNew, or Truncate.


mode is OpenOrCreate and the file on disk does not exist.


An I/O error occurred.


path exceeds the maximum length defined by the operating system. In Windows, paths must contain fewer than 248 characters, and file names must contain fewer than 260 characters.


The caller does not have the required permissions for the file.

The mode parameter pertains to the source file on disk. You can use only the Open enumeration value to create the memory-mapped file from the source file on disk.

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.