MemoryMappedFile.CreateOrOpen Method (String, Int64)

.NET Framework (current version)

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Creates or opens a memory-mapped file that has the specified capacity in system memory.

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

public static MemoryMappedFile CreateOrOpen(
	string mapName,
	long capacity


Type: System.String

A name to assign to the memory-mapped file.

Type: System.Int64

The maximum size, in bytes, to allocate to the memory-mapped file.

Return Value

Type: System.IO.MemoryMappedFiles.MemoryMappedFile

A memory-mapped file that has the specified name and size.

Exception Condition

mapName is an empty string.


mapName is null.


capacity is greater than the size of the logical address space.


capacity is less than or equal to zero.

Use this method to create or open a memory-mapped file that is not persisted (that is, not associated with a file on disk), which you can use to share data between processes.

.NET Framework
Available since 4.0
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