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Marshal.ReadByte Method (IntPtr)

Reads a single byte from unmanaged memory.

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

Public Shared Function ReadByte ( _
	ptr As IntPtr _
) As Byte


Type: System.IntPtr

The address in unmanaged memory from which to read.

Return Value

Type: System.Byte
The byte read from unmanaged memory.


ptr is not a recognized format.


ptr is Nothing.


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.

Reading from unaligned memory locations is supported.

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

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

using namespace System;
using namespace System::Runtime::InteropServices;

void main()
	// Create an unmanaged byte. 
	const char * myString = "b";

	// Read the c string as a managed byte.
        Byte ^ myManagedByte = Marshal::ReadByte((IntPtr) (char *) myString);

	// Display the byte to the console.

.NET Framework

Supported in: 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

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, 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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