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Marshal.ReadInt64 Method (IntPtr)

Reads a 64-bit signed integer from unmanaged memory.

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

public static long ReadInt64(
	IntPtr ptr
)

Parameters

ptr
Type: System.IntPtr

The address in unmanaged memory from which to read.

Return Value

Type: System.Int64
The 64-bit signed integer read from unmanaged memory.

ExceptionCondition
AccessViolationException

ptr is not a recognized format.

-or-

ptr is null.

-or-

ptr is invalid.

ReadInt64 has an implied offset of 0. This method enables direct interaction with an unmanaged C-style Int64 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));
    }

    Marshal.FreeHGlobal(unmanagedArray);

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

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.
	__int64 myVal = 42;

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

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

.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

XNA Framework

Supported in: 3.0, 2.0, 1.0

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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