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Marshal.WriteInt32 Method (IntPtr, Int32, Int32)

Writes a 32-bit signed integer value into unmanaged memory at a specified offset.

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

'Declaration
Public Shared Sub WriteInt32 ( _
	ptr As IntPtr, _
	ofs As Integer, _
	val As Integer _
)

Parameters

ptr
Type: System.IntPtr

The base address in unmanaged memory to write to.

ofs
Type: System.Int32

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

val
Type: System.Int32

The value to write.

ExceptionCondition
AccessViolationException

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

WriteInt32 enables direct interaction with an unmanaged 32-bit signed array, eliminating the expense of copying an entire unmanaged array (using Marshal.Copy) to a separate managed array before setting its element values.

Writing to 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

.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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