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Marshal.WriteIntPtr Method (IntPtr, Int32, IntPtr)

Writes a processor native-sized integer value to unmanaged memory at a specified offset.

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

public static void WriteIntPtr(
	IntPtr ptr,
	int ofs,
	IntPtr val
)

Parameters

ptr
Type: System.IntPtr

The base address in unmanaged memory to write to.

ofs
Type: System.Int32

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

val
Type: System.IntPtr

The value to write.

ExceptionCondition
AccessViolationException

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

This method writes a 32 bit integer on 32 bit systems, and a 64 bit integer on 64 bit systems.

WriteIntPtr enables direct interaction with an unmanaged C-style IntPtr array, eliminating the expense of copying an entire unmanaged array (using Marshal.Copy) to a separate managed array before setting its element values.

Writing to unaligned memory locations is supported.

The following example demonstrates how to read and write to an unmanaged array using the ReadIntPtr and WriteIntPtr methods.

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

    // Set the 10 elements of the C-style unmanagedArray 
    for (int i = 0; i < 10; i++)
    {
        Marshal.WriteIntPtr(unmanagedArray, i * elementSize, ((IntPtr)(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.ReadIntPtr(unmanagedArray, i * elementSize));
    }

    Marshal.FreeHGlobal(unmanagedArray);

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

  • SecurityCriticalAttribute 

    requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

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