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Marshal.ReadInt32 Method (IntPtr)

Reads a 32-bit signed integer from unmanaged memory.

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

public static int ReadInt32 (
	IntPtr ptr
)
public static int ReadInt32 (
	IntPtr ptr
)
public static function ReadInt32 (
	ptr : IntPtr
) : int
Not applicable.

Parameters

ptr

The address in unmanaged from which to read.

Return Value

The 32-bit signed integer read from the ptr parameter.

Exception typeCondition

AccessViolationException

ptr is not a recognized format.

-or-

ptr is a null reference (Nothing in Visual Basic).

-or-

ptr is invalid.

ReadInt32 has an implied offset of 0. This method enables direct interaction with an unmanaged C-style Int32 array, eliminating the expense of copying an entire unmanaged array (using Marshal.Copy) to a separate managed array before reading 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 ReadInt32 and WriteInt32 methods.

static void ReadWriteInt32()
{
    // Allocate unmanaged memory. 
    IntPtr unmanagedArray = Marshal.AllocHGlobal(10);

    // One way to set the 10 elements of the C-style unmanagedArray
    Int32[] newArray = new Int32[10];


    // Set the 10 elements of the C-style unmanagedArray
    for (int i = 0; i < 10; i++)
    {
        Marshal.WriteInt32(unmanagedArray, i * Marshal.SizeOf(typeof(Int32)), ((Int32)(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.ReadInt32(unmanagedArray, i * Marshal.SizeOf(typeof(Int32))));
    }

    Marshal.FreeHGlobal(unmanagedArray);

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

}

The following code example demonstrates how to use the ReadInt32 method to read the value of an unmanaged int variable.

using namespace System;
using namespace System::Runtime::InteropServices;



void main()
{
	// Create an unmanaged integer.
	int myVal = 42;

	// Read the int as a managed Int32.
        Int32 ^ myManagedVal = Marshal::ReadInt32((IntPtr) &myVal);

	// Display the value to the console.
	Console::WriteLine(myManagedVal);
}

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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