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Showing content from https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.marshal.ptrtostructure below:

Marshal.PtrToStructure Method (System.Runtime.InteropServices) | Microsoft Learn

Source:: Marshal.cs

Source:: Marshal.cs

Source:: Marshal.cs

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);

[System.Obsolete("PtrToStructure(IntPtr, Type) may be unavailable in future releases. Instead, use PtrToStructure<T>(IntPtr). For more info, go to http://go.microsoft.com/fwlink/?LinkID=296513")]
[System.Security.SecurityCritical]
public static object PtrToStructure(IntPtr ptr, Type structureType);

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

[System.Security.SecurityCritical]
public static object PtrToStructure(IntPtr ptr, Type structureType);

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

[System.Runtime.InteropServices.ComVisible(true)]
public static object PtrToStructure(IntPtr ptr, Type structureType);

[System.Security.SecurityCritical]
[System.Runtime.InteropServices.ComVisible(true)]
public static object PtrToStructure(IntPtr ptr, Type structureType);

[<System.Obsolete("PtrToStructure(IntPtr, Type) may be unavailable in future releases. Instead, use PtrToStructure<T>(IntPtr). For more info, go to http://go.microsoft.com/fwlink/?LinkID=296513")>]
[<System.Security.SecurityCritical>]
static member PtrToStructure : nativeint * Type -> obj

static member PtrToStructure : nativeint * Type -> obj

[<System.Security.SecurityCritical>]
static member PtrToStructure : nativeint * Type -> obj

[<System.Runtime.InteropServices.ComVisible(true)>]
static member PtrToStructure : nativeint * Type -> obj

[<System.Security.SecurityCritical>]
[<System.Runtime.InteropServices.ComVisible(true)>]
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

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

Attributes

Exceptions

The structureType parameter layout is not sequential or explicit.

-or-

The structureType parameter is a generic type definition.

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.

[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.