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.

Exception Condition

ptr is not a recognized format.


ptr is null.


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

Module Example
    Sub Main()
         ' 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: {0}", 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: {0}", c)

         ' Free the unmanaged memory.
         Console.WriteLine("Unmanaged memory was disposed.")
    End Sub
End Module


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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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