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Marshal.ReadByte Method (IntPtr, Int32)

Reads a single byte at a given offset (or index) from unmanaged memory.

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

public static byte ReadByte(
	IntPtr ptr,
	int ofs
)

Parameters

ptr
Type: System.IntPtr

The base address in unmanaged memory from which to read.

ofs
Type: System.Int32

An additional byte offset, which is added to the ptr parameter before reading.

Return Value

Type: System.Byte
The byte read from unmanaged memory at the given offset.

ExceptionCondition
AccessViolationException

Base address (ptr) plus offset byte (ofs) produces a null or invalid address.

ReadByte 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 demonstrates how to read and write to an unmanaged array using the ReadByte and WriteByte methods.

static void ReadWriteByte()
{
    // Allocate unmanaged memory.  
    int elementSize = 1;
    IntPtr unmanagedArray = Marshal.AllocHGlobal(10 * elementSize);

    // Set the 10 elements of the C-style unmanagedArray 
    for (int i = 0; i < 10; i++)
    {
        Marshal.WriteByte(unmanagedArray, i * elementSize, ((Byte)(i + 1)));
    }
    Console.WriteLine("Unmanaged memory written.");

    Console.WriteLine("Reading unmanaged memory:");
    // Print the 10 elements of the C-style unmanagedArray 
    for (int i = 0; i < 10; i++)
    {
        Console.WriteLine(Marshal.ReadByte(unmanagedArray, i * elementSize));
    }

    Marshal.FreeHGlobal(unmanagedArray);

    Console.WriteLine("Done. Press Enter to continue.");
    Console.ReadLine();
}

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 = "bB";

	// Read the second character of the c string as a managed byte.
        Byte ^ myManagedByte = Marshal::ReadByte((IntPtr) (char *) myString, 1);

	// Display the byte to the console.
	Console::WriteLine(myManagedByte);
}

.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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