ReadInt64 Method (IntPtr, Int32)

Marshal.ReadInt64 Method (IntPtr, Int32)


Reads a 64-bit signed integer at a given offset from unmanaged memory.

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

public static long ReadInt64(
	IntPtr ptr,
	int ofs


Type: System.IntPtr

The base address in unmanaged memory from which to read.

Type: System.Int32

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

Return Value

Type: System.Int64

The 64-bit signed integer read from unmanaged memory at the given offset.

Exception Condition

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

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.

Reading from unaligned memory locations is supported.

The following example demonstrates how to read and write to an unmanaged array using the ReadInt64 and WriteInt64 methods.

static void ReadWriteInt64()
    // Allocate unmanaged memory. 
    int elementSize = 8;
    IntPtr unmanagedArray = Marshal.AllocHGlobal(10 * elementSize);

    // Set the 10 elements of the C-style unmanagedArray
    for (int i = 0; i < 10; i++)
        Marshal.WriteInt64(unmanagedArray, i * elementSize, ((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 * elementSize));


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

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

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

void main()
    // Create an unmanaged __int64 pointer.
    __int64 * myVal;
    __int64 tmp = 42;
    // Initialize it to another value.
    myVal = &tmp;

    // Read value as a managed Int64.
    Int64 ^ myManagedVal = Marshal::ReadInt64((IntPtr) myVal, 0);

    // Display the value to the console.


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

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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