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Marshal.WriteByte Method (IntPtr, Byte)

Writes a single byte value to unmanaged memory.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

Public Shared Sub WriteByte ( _
	ptr As IntPtr, _
	val As Byte _


Type: System.IntPtr

The address in unmanaged memory to write to.

Type: System.Byte

The value to write.


ptr is not a recognized format.


ptr is Nothing.


ptr is invalid.

WriteByte enables direct interaction with an unmanaged C-style byte array, eliminating the expense of copying an entire unmanaged array (using Marshal.Copy) to a separate managed array before setting its element values.

The following example creates a block of unmanaged memory, writes a byte to the unmanaged memory, reads the byte back from unmanaged memory, and then disposes the unmanaged memory.

Imports System
Imports System.Runtime.InteropServices

Class MarshalExample

    Shared Sub Main(ByVal args() As String) 

            ' Allocate 1 byte of unmanaged memory. 
            Dim hGlobal As IntPtr = Marshal.AllocHGlobal(1)

            ' Create a new byte. 
            Dim b As Byte = 1

            Console.WriteLine("Byte written to unmanaged memory: " + b)

            ' Write the byte to unmanaged memory.
            Marshal.WriteByte(hGlobal, b)

            ' Read byte from unmanaged memory. 
            Dim c As Byte = Marshal.ReadByte(hGlobal)

            Console.WriteLine("Byte read from unmanaged memory: " + c)

            ' Free the unmanaged memory.

            Console.Write("Unmanaged memory was disposed.")

        Catch e As Exception
        End Try


    End Sub  
End Class

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

  • SecurityCriticalAttribute 

    requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Windows Phone 8.1, Windows Phone 8, 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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