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Marshal.WriteByte Method (Object, Int32, Byte)

Writes a single byte value to unmanaged memory.

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

public static void WriteByte (
	[InAttribute] [OutAttribute] Object ptr,
	int ofs,
	byte val
public static void WriteByte (
	/** @attribute InAttribute() */ /** @attribute OutAttribute() */ Object ptr, 
	int ofs, 
	byte val
public static function WriteByte (
	ptr : Object, 
	ofs : int, 
	val : byte
Not applicable.



The base address in unmanaged memory of the target object.


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


The value to write.

Exception typeCondition


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


ptr is an ArrayWithOffset object. This method does not accept ArrayWithOffset parameters.

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.


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.

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

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