Marshal.ReadByte Method (IntPtr)

Reads a single byte from an unmanaged pointer.

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

public static byte ReadByte (
	IntPtr ptr
public static byte ReadByte (
	IntPtr ptr
public static function ReadByte (
	ptr : IntPtr
) : byte



The address in unmanaged memory from which to read.

Return Value

The byte read from the ptr parameter.

Exception typeCondition


ptr is not a recognized format.


ptr is a null reference (Nothing in Visual Basic).


ptr is invalid.

ReadByte has an implied offset of 0. This method 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 reading its element values.


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)

                // 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.

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

            catch (Exception e)



The following code example demonstrates how to use the ReadByte method to read the value of an unmanaged character.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0