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Marshal.ReadIntPtr Method (IntPtr, Int32)

Reads a processor native sized integer at a given offset from unmanaged memory.

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

public static IntPtr ReadIntPtr(
	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.IntPtr
The integer read from unmanaged memory at the given offset.

ExceptionCondition
AccessViolationException

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

ReadIntPtr 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 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 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

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.

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