MemoryMappedFile.OpenExisting Method (String)
Opens an existing memory-mapped file that has the specified name in system memory.
Assembly: System.Core (in System.Core.dll)
'Declaration Public Shared Function OpenExisting ( _ mapName As String _ ) As MemoryMappedFile
- Type: System.String
The name of the memory-mapped file to open.
Return ValueType: System.IO.MemoryMappedFiles.MemoryMappedFile
A memory-mapped file that has the specified name.
Opening a Persisted Memory-Mapped File
The following example opens a memory-mapped file named ImgA that has already been created from a file on disk (as shown in the example for the CreateFromFile(String) method).
Imports System Imports System.IO.MemoryMappedFiles Imports System.Runtime.InteropServices Class Program Public Shared Sub Main(ByVal args As String()) ' Assumes another process has created the memory-mapped file. Using mmf = MemoryMappedFile.OpenExisting("ImgA") Using accessor = mmf.CreateViewAccessor(4000000, 2000000) Dim colorSize As Integer = Marshal.SizeOf(GetType(MyColor)) Dim color As MyColor ' Make changes to the view. Dim i As Long = 0 While i < 1500000 accessor.Read(i, color) color.Brighten(30) accessor.Write(i, color) i += colorSize End While End Using End Using End Sub End Class Public Structure MyColor Public Red As Short Public Green As Short Public Blue As Short Public Alpha As Short ' Make the view brigher. Public Sub Brighten(ByVal value As Short) Red = CShort(Math.Min(Short.MaxValue, CInt(Red) + value)) Green = CShort(Math.Min(Short.MaxValue, CInt(Green) + value)) Blue = CShort(Math.Min(Short.MaxValue, CInt(Blue) + value)) Alpha = CShort(Math.Min(Short.MaxValue, CInt(Alpha) + value)) End Sub End Structure
Opening a Non-Persisted Memory-Mapped File
The following example opens a memory-mapped file used for inter-process communication. This code example is part of a larger example provided for the CreateNew(String, Int64) method.
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.