Marshal.PtrToStructure Method

Definition

Namespace:

System.Runtime.InteropServices

Assembly:

System.Runtime.InteropServices.dll

Marshals data from an unmanaged block of memory to a managed object.

Overloads

PtrToStructure(IntPtr, Object)	Marshals data from an unmanaged block of memory to a managed object.
PtrToStructure(IntPtr, Type)	Marshals data from an unmanaged block of memory to a newly allocated managed object of the specified type.
PtrToStructure<T>(IntPtr)	Marshals data from an unmanaged block of memory to a newly allocated managed object of the type specified by a generic type parameter.
PtrToStructure<T>(IntPtr, T)	Marshals data from an unmanaged block of memory to a managed object of the specified type.

PtrToStructure(IntPtr, Object)

Source:

Marshal.cs

Marshals data from an unmanaged block of memory to a managed object.

public:
 static void PtrToStructure(IntPtr ptr, System::Object ^ structure);

public static void PtrToStructure (IntPtr ptr, object structure);

static member PtrToStructure : nativeint * obj -> unit

Public Shared Sub PtrToStructure (ptr As IntPtr, structure As Object)

Parameters

ptr

IntPtr

nativeint

A pointer to an unmanaged block of memory.

structure

Object

The object to which the data is to be copied. This must be an instance of a formatted class.

Exceptions

ArgumentException

Structure layout is not sequential or explicit.

-or-

Structure is a boxed value type.

Remarks

PtrToStructure is often necessary in COM interop and platform invoke when structure parameters are represented as an System.IntPtr value. You cannot use this overload method with value types. If the ptr parameter equals IntPtr.Zero, null will be returned.

PtrToStructure(IntPtr, Type)

Source:

Marshal.cs

Marshals data from an unmanaged block of memory to a newly allocated managed object of the specified type.

public:
 static System::Object ^ PtrToStructure(IntPtr ptr, Type ^ structureType);

public static object? PtrToStructure (IntPtr ptr, Type structureType);

static member PtrToStructure : nativeint * Type -> obj

Public Shared Function PtrToStructure (ptr As IntPtr, structureType As Type) As Object

Parameters

ptr

IntPtr

nativeint

A pointer to an unmanaged block of memory.

structureType

Type

The type of object to be created. This object must represent a formatted class or a structure.

Returns

Object

A managed object containing the data pointed to by the ptr parameter.

Exceptions

ArgumentException

The structureType parameter layout is not sequential or explicit.

-or-

The structureType parameter is a generic type definition.

ArgumentNullException

structureType is null.

MissingMethodException

The class specified by structureType does not have an accessible parameterless constructor.

Examples

The following example creates a managed structure, transfers it to unmanaged memory, and then transfers it back to managed memory using the PtrToStructure method.

using System;
using System.Runtime.InteropServices;

public struct Point
{
    public int x;
    public int y;
}

class Example
{

    static void Main()
    {

        // Create a point struct.
        Point p;
        p.x = 1;
        p.y = 1;

        Console.WriteLine("The value of first point is " + p.x + " and " + p.y + ".");

        // Initialize unmanged memory to hold the struct.
        IntPtr pnt = Marshal.AllocHGlobal(Marshal.SizeOf(p));

        try
        {

            // Copy the struct to unmanaged memory.
            Marshal.StructureToPtr(p, pnt, false);

            // Create another point.
            Point anotherP;

            // Set this Point to the value of the
            // Point in unmanaged memory.
            anotherP = (Point)Marshal.PtrToStructure(pnt, typeof(Point));

            Console.WriteLine("The value of new point is " + anotherP.x + " and " + anotherP.y + ".");
        }
        finally
        {
            // Free the unmanaged memory.
            Marshal.FreeHGlobal(pnt);
        }
    }
}

Imports System.Runtime.InteropServices



Public Structure Point
    Public x As Integer
    Public y As Integer
End Structure


Module Example


    Sub Main()

        ' Create a point struct.
        Dim p As Point
        p.x = 1
        p.y = 1

        Console.WriteLine("The value of first point is " + p.x.ToString + " and " + p.y.ToString + ".")

        ' Initialize unmanged memory to hold the struct.
        Dim pnt As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(p))

        Try

            ' Copy the struct to unmanaged memory.
            Marshal.StructureToPtr(p, pnt, False)

            ' Create another point.
            Dim anotherP As Point

            ' Set this Point to the value of the 
            ' Point in unmanaged memory. 
            anotherP = CType(Marshal.PtrToStructure(pnt, GetType(Point)), Point)

            Console.WriteLine("The value of new point is " + anotherP.x.ToString + " and " + anotherP.y.ToString + ".")

        Finally
            ' Free the unmanaged memory.
            Marshal.FreeHGlobal(pnt)
        End Try

    End Sub
End Module

The following example demonstrates how to marshal an unmanaged block of memory to a managed structure using the PtrToStructure method.

Important

This code assumes 32-bit compilation. Before using a 64-bit compiler, replace IntPtr.ToInt32 with IntPtr.ToInt64.

[StructLayout(LayoutKind::Sequential)]
ref class INNER
{
public:
    [MarshalAs(UnmanagedType::ByValTStr,SizeConst=10)]
    String^ field;

    INNER()
    {
        field = "Test";
    }
};

[StructLayout(LayoutKind::Sequential)]
value struct OUTER
{
public:
    [MarshalAs(UnmanagedType::ByValTStr,SizeConst=10)]
    String^ field;

    [MarshalAs(UnmanagedType::ByValArray,SizeConst=100)]
    array<Byte>^ inner;
};

[DllImport("SomeTestDLL.dll")]
static void CallTest(OUTER^ outerStructurePointer);

void static Work()
{
    OUTER outerStructure;
    array<INNER^>^ innerArray = gcnew array<INNER^>(10);
    INNER^ innerStructure = gcnew INNER;
    int structSize = Marshal::SizeOf(innerStructure);
    int size = innerArray->Length * structSize;
    outerStructure.inner = gcnew array<Byte>(size);

    try
    {
        CallTest(outerStructure);
    }
    catch (SystemException^ ex) 
    {
        Console::WriteLine(ex->Message);
    }

    IntPtr buffer = Marshal::AllocCoTaskMem(structSize * 10);
    Marshal::Copy(outerStructure.inner, 0, buffer, structSize * 10);
    int currentOffset = 0;
    for (int i = 0; i < 10; i++)
    {
        innerArray[i] = safe_cast<INNER^>(Marshal::PtrToStructure(
            IntPtr(buffer.ToInt32() + currentOffset),
            INNER::typeid));
        currentOffset += structSize;
    }
    Console::WriteLine(outerStructure.field);
    Marshal::FreeCoTaskMem(buffer);
}

        [StructLayout(LayoutKind.Sequential)]

        public class  INNER

        {

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst =  10)]

            public string field1 = "Test";
        }	

        [StructLayout(LayoutKind.Sequential)]

        public struct OUTER

        {

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst =  10)]

            public string field1;

            [MarshalAs(UnmanagedType.ByValArray, SizeConst =  100)]

            public byte[] inner;
        }
        [DllImport(@"SomeTestDLL.dll")]

        public static extern void CallTest( ref OUTER po);
        static void Main(string[] args)

        {

            OUTER ed = new OUTER();

            INNER[] inn=new INNER[10];

            INNER test = new INNER();

            int iStructSize = Marshal.SizeOf(test);
            int sz =inn.Length * iStructSize;

            ed.inner = new byte[sz];
            try

            {

                CallTest( ref ed);
            }

            catch(Exception e)

            {

                Console.WriteLine(e.Message);
            }

            IntPtr buffer = Marshal.AllocCoTaskMem(iStructSize*10);

            Marshal.Copy(ed.inner,0,buffer,iStructSize*10);
            int iCurOffset = 0;

            for(int i=0;i<10;i++)

            {
                inn[i] = (INNER)Marshal.PtrToStructure(new
IntPtr(buffer.ToInt32()+iCurOffset),typeof(INNER) );

                iCurOffset += iStructSize;
            }

            Console.WriteLine(ed.field1);

            Marshal.FreeCoTaskMem(buffer);
        }

Remarks

PtrToStructure is often necessary in COM interop and platform invoke when structure parameters are represented as an System.IntPtr value. You can pass a value type to this overload method. In this case, the returned object is a boxed instance. If the ptr parameter equals IntPtr.Zero, null will be returned.

See also

• GetTypeAttr(IntPtr)

PtrToStructure<T>(IntPtr)

Source:

Marshal.cs

Marshals data from an unmanaged block of memory to a newly allocated managed object of the type specified by a generic type parameter.

public:
generic <typename T>
 static T PtrToStructure(IntPtr ptr);

public static T? PtrToStructure<T> (IntPtr ptr);

static member PtrToStructure : nativeint -> 'T

Public Shared Function PtrToStructure(Of T) (ptr As IntPtr) As T

Type Parameters

T

The type of the object to which the data is to be copied. This must be a formatted class or a structure.

Parameters

ptr

IntPtr

nativeint

A pointer to an unmanaged block of memory.

Returns

T

A managed object that contains the data that the ptr parameter points to.

Exceptions

ArgumentException

The layout of T is not sequential or explicit.

MissingMethodException

The class specified by T does not have an accessible parameterless constructor.

Remarks

PtrToStructure<T>(IntPtr) is often necessary in COM interop and platform invoke when structure parameters are represented as System.IntPtr values. You can pass a value type to this method overload. If the ptr parameter equals IntPtr.Zero and T is a reference type, null is returned. If ptr equals IntPtr.Zero and T is a value type, a NullReferenceException is thrown.

PtrToStructure<T>(IntPtr, T)

Source:

Marshal.cs

Marshals data from an unmanaged block of memory to a managed object of the specified type.

public:
generic <typename T>
 static void PtrToStructure(IntPtr ptr, T structure);

public static void PtrToStructure<T> (IntPtr ptr, T structure);

static member PtrToStructure : nativeint * 'T -> unit

Public Shared Sub PtrToStructure(Of T) (ptr As IntPtr, structure As T)

Type Parameters

T

The type of structure. This must be a formatted class.

Parameters

ptr

IntPtr

nativeint

A pointer to an unmanaged block of memory.

structure

T

The object to which the data is to be copied.

Exceptions

ArgumentException

Structure layout is not sequential or explicit.

Remarks

PtrToStructure<T>(IntPtr, T) is often necessary in COM interop and platform invoke when structure parameters are represented as IntPtr values. You cannot use this method overload with value types. If the ptr parameter equals IntPtr.Zero and T is a reference type, null is returned. If ptr equals IntPtr.Zero and T is a value type, a NullReferenceException is thrown.