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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)

[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
public static void WriteByte(
	IntPtr ptr,
	byte val
)

Parameters

ptr
Type: System.IntPtr

The address in unmanaged to write.

val
Type: System.Byte

The value to write.

ExceptionCondition
AccessViolationException

ptr is not a recognized format.

-or-

ptr is null.

-or-

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.

NoteNote:

This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

The following code 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.

using System;
using System.Runtime.InteropServices;


namespace SecureStringExample
{

    class MarshalExample
    {


        static void Main(string[] args)
        {

            try
            {
                // Allocate 1 byte of unmanaged memory.
                IntPtr hGlobal = Marshal.AllocHGlobal(1);

                // Create a new byte.
                byte b = 1;

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

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

                // Read byte from unmanaged memory.
                byte c = Marshal.ReadByte(hGlobal);

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

                // Free the unmanaged memory.
                Marshal.FreeHGlobal(hGlobal);

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


            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }

            Console.Read();

        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
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