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Marshal.WriteByte Method (IntPtr, Int32, Byte)

Writes a single byte value to unmanaged memory.

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

public static void WriteByte (
	IntPtr ptr,
	int ofs,
	byte val
)
public static void WriteByte (
	IntPtr ptr, 
	int ofs, 
	byte val
)
public static function WriteByte (
	ptr : IntPtr, 
	ofs : int, 
	val : byte
)
Not applicable.

Parameters

ptr

The base address in unmanaged memory to write.

ofs

An additional byte offset, added to the ptr parameter before writing.

val

The value to write.

Exception typeCondition

AccessViolationException

Base address (ptr) plus offset byte (ofs) produces a a null reference (Nothing in Visual Basic) or invalid address.

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

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

    // One way to set the 10 elements of the C-style unmanagedArray
    Byte[] newArray = new Byte[10];


    // Set the 10 elements of the C-style unmanagedArray
    for (int i = 0; i < 10; i++)
    {
        Marshal.WriteByte(unmanagedArray, i * Marshal.SizeOf(typeof(Byte)), ((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 * Marshal.SizeOf(typeof(Byte))));
    }

    Marshal.FreeHGlobal(unmanagedArray);

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

}

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0
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