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MemoryMappedFile.CreateFromFile Method (FileStream, String, Int64, MemoryMappedFileAccess, MemoryMappedFileSecurity, HandleInheritability, Boolean)

Creates a memory-mapped file that has the specified name, capacity, access type, security permissions, inheritability, and disposal requirement from a file on disk.

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

'Declaration
<SecurityPermissionAttribute(SecurityAction.Demand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
Public Shared Function CreateFromFile ( _
	fileStream As FileStream, _
	mapName As String, _
	capacity As Long, _
	access As MemoryMappedFileAccess, _
	memoryMappedFileSecurity As MemoryMappedFileSecurity, _
	inheritability As HandleInheritability, _
	leaveOpen As Boolean _
) As MemoryMappedFile

Parameters

fileStream
Type: System.IO.FileStream

The fileStream to the file to map.

mapName
Type: System.String

A name to assign to the memory-mapped file.

capacity
Type: System.Int64

The maximum size, in bytes, to allocate to the memory-mapped file. Specify 0 to set the capacity to the size of the file on disk.

access
Type: System.IO.MemoryMappedFiles.MemoryMappedFileAccess

One of the enumeration values that specifies the type of access allowed to the memory-mapped file. The default is ReadWrite.

This parameter cannot be set to Read or Write.

memoryMappedFileSecurity
Type: System.IO.MemoryMappedFiles.MemoryMappedFileSecurity

The permissions that can be granted for file access and operations on memory-mapped files.

This parameter can be Nothing.

inheritability
Type: System.IO.HandleInheritability

One of the enumeration values that specifies whether a handle to the memory-mapped file can be inherited by a child process. The default is None.

leaveOpen
Type: System.Boolean

true to not dispose fileStream after the MemoryMappedFile is closed; false to dispose fileStream.

Return Value

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

ExceptionCondition
ArgumentException

mapName is an empty string.

-or-

capacity and the length of the file are zero.

-or-

access is set to the Read or Write enumeration value, which is not allowed.

ArgumentNullException

fileStream or mapname is Nothing.

ArgumentOutOfRangeException

capacity is less than zero.

-or-

capacity is less than the file size.

-or-

access is not a valid MemoryMappedFileAccess enumeration value.

-or-

inheritability is not a valid HandleInheritability enumeration value.

ObjectDisposedException

fileStream was closed.

UnauthorizedAccessException

access is set to MemoryMappedFileAccess.ReadWrite when fileStream's access is set to FileAccess.Read or FileAccess.Write.

IOException

mapName already exists.

If capacity is larger than the size of the file on disk, the file on disk is increased to match the specified capacity even if no data is written to the memory-mapped file. To prevent this from occurring, specify 0 (zero) for the default capacity, which will internally set capacity to the size of the file on disk.

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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