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Marshal.Copy Method (IntPtr, Char(), Int32, Int32)

Copies data from an unmanaged memory pointer to a managed character array.

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

Public Shared Sub Copy ( _
	source As IntPtr, _
	destination As Char(), _
	startIndex As Integer, _
	length As Integer _


Type: System.IntPtr

The memory pointer to copy from.

Type: System.Char()

The array to copy to.

Type: System.Int32

The zero-based index in the destination array where copying should start.

Type: System.Int32

The number of array elements to copy.


source, destination, startIndex, or length is Nothing.

Unmanaged, C-style arrays do not contain bounds information, which prevents the startIndex and length parameters from being validated. Thus, the unmanaged data corresponding to the source parameter populates the managed array regardless of its usefulness. You must initialize the managed array with the appropriate size before calling this method.

The following example copies an array to unmanaged memory and then copies the unmanaged array back to managed memory.

' Remember that the actual size of System.Char in unmanaged memory is 2. 

Imports System
Imports System.Runtime.InteropServices

Module Module1

    Sub Main()
        ' Create a managed array. 
        Dim managedArray As Char() = New Char(999) {}
        managedArray(0) = "a"c
        managedArray(1) = "b"c
        managedArray(2) = "c"c
        managedArray(3) = "d"c
        managedArray(999) = "Z"c

        ' Initialize unmanaged memory to hold the array. 
        ' Dim size As Integer = Marshal.SizeOf(managedArray[0]) * managedArray.Length;  ' Incorrect 
        Dim size As Integer = Marshal.SystemDefaultCharSize * managedArray.Length       ' Correct

        Dim pnt As IntPtr = Marshal.AllocHGlobal(size)

            ' Copy the array to unmanaged memory.
            Marshal.Copy(managedArray, 0, pnt, managedArray.Length)

            ' Copy the unmanaged array back to another managed array. 

            Dim managedArray2 As Char() = New Char(managedArray.Length - 1) {}

            Marshal.Copy(pnt, managedArray2, 0, managedArray.Length)
            Console.WriteLine("Here is the roundtripped array: {0} {1} {2} {3} {4}", managedArray2(0), managedArray2(1), managedArray2(2), managedArray2(3), managedArray2(999))

            Console.WriteLine("The array was copied to unmanaged memory and back.")
            ' Free the unmanaged memory.

        End Try 
    End Sub 
End Module

.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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