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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)

'Declaration
Public Shared Function ReadInt64 ( _
	ptr As IntPtr _
) As Long

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 Nothing.

-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.

Sub ReadWriteInt64()
    ' Allocate unmanaged memory.  
    Dim elementSize As Integer = 8
    Dim unmanagedArray As IntPtr = Marshal.AllocHGlobal(10 * elementSize)

    ' Set the 10 elements of the C-style unmanagedArray 
    For i As Integer = 0 To 9
        Marshal.WriteInt64(unmanagedArray, i * elementSize, CType(i + 1, Int64))
    Next i
    Console.WriteLine("Unmanaged memory written.")

    Console.WriteLine("Reading unmanaged memory:")
    ' Print the 10 elements of the C-style unmanagedArray 
    For i As Integer = 0 To 9
        Console.WriteLine(Marshal.ReadInt64(unmanagedArray, i * elementSize))
    Next i

    Marshal.FreeHGlobal(unmanagedArray)

    Console.WriteLine("Done. Press Enter to continue.")
    Console.ReadLine()
End Sub

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, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

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.

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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