This documentation is archived and is not being maintained.

Marshal.ReadInt64 Method (IntPtr, Int32)

Reads a 64-bit signed integer from unmanaged memory.

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

public static long ReadInt64 (
	IntPtr ptr,
	int ofs
)
public static long ReadInt64 (
	IntPtr ptr, 
	int ofs
)
public static function ReadInt64 (
	ptr : IntPtr, 
	ofs : int
) : long

Parameters

ptr

The base address in unmanaged memory from which to read.

ofs

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

Return Value

The 64-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.

ReadInt64 enables direct interaction with an unmanaged 64-bit signed 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 ReadInt64 and WriteInt64 methods.

static void ReadWriteInt64()
{
    // Allocate unmanaged memory. 
    IntPtr unmanagedArray = Marshal.AllocHGlobal(10);

    // One way to set the 10 elements of the C-style unmanagedArray
    Int64[] newArray = new Int64[10];


    // Set the 10 elements of the C-style unmanagedArray
    for (int i = 0; i < 10; i++)
    {
        Marshal.WriteInt64(unmanagedArray, i * Marshal.SizeOf(typeof(Int64)), ((Int64)(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.ReadInt64(unmanagedArray, i * Marshal.SizeOf(typeof(Int64))));
    }

    Marshal.FreeHGlobal(unmanagedArray);

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

}

The following code example demonstrates how to use the ReadInt64 method to read the value of an unmanaged __int64 variable.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0
Show: