Marshal.ReadInt32 Method (IntPtr)

 

Reads a 32-bit signed integer from unmanaged memory.

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

<SecurityCriticalAttribute>
Public Shared Function ReadInt32 (
	ptr As IntPtr
) As Integer

Parameters

ptr
Type: System.IntPtr

The address in unmanaged memory from which to read.

Return Value

Type: System.Int32

The 32-bit signed integer read from unmanaged memory.

Exception Condition
AccessViolationException

ptr is not a recognized format.

-or-

ptr is null.

-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.

Reading from unaligned memory locations is supported.

The following example demonstrates how to read and write to an unmanaged array using the ReadInt32 and WriteInt32 methods.

Sub ReadWriteInt32()
    ' Allocate unmanaged memory. 
    Dim elementSize As Integer = 4
    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.WriteInt32(unmanagedArray, i * elementSize, CType(i + 1, Int32))
    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.ReadInt32(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 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);
}

SecurityCriticalAttribute

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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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