How to pass a ref struct in delegate from WPF application to C++ DLL

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C++

C#

XAML

WPF

PInvoke

DLL

I am currently using delegate from c# to C++ dll i am passing the ref struct to get the value of struct from c++ dll,with out using call back i can able to get the struct value using marshalling.but for dynamic purpose i am using Delegate callback.
while i am working i dont know in callback what i need to use i am facing the issue

if i use without ref in update() method

Quote:

Error CS1676 Parameter 1 must be declared with the 'ref' keyword

if i am not using ref in update() method

Quote:

Error CS0246 The type or namespace name 'strNode' could not be found

What I have tried:

In C#

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct NODE
    {
        public ulong ullSector;
        public ulong ullSize;

        unsafe public NODE* pNext;
        unsafe public NODE* pChild;
        unsafe public NODE* pParent;

        public uint dwID;
        public uint dwSelfNum;
        public uint dwParentNum;

        public IntPtr pwcName;
}

above one is my struct

public delegate void ProgressCallback(ref NODE strNode);
    public delegate string GetFilePathCallback(string filter);

  public async void update()
        {
         

            ProgressCallback callback =
                (  ref strNode) => //Here the issues rising
                {
                    Application.Current.Dispatcher.Invoke((Action)delegate
                    {

                        
                      Console.WriteLine("Progress = {0}", strNode.Name.ToString());
                    });
                };

            // call DoWork in C code
            DoWork(callback);
        }

in my c++ dll
XXXX.h

#ifdef __cplusplus
extern "C"
{
#endif

#define DLL __declspec(dllexport)
    typedef void(__stdcall* ProgressCallback)(NODE*);
    typedef char* (__stdcall* GetFilePathCallback)(char* filter);

    DLL void DoWork(ProgressCallback progressCallback);
    DLL void ProcessFile(GetFilePathCallback getPath);

#ifdef __cplusplus
}
#endif

XXXX.cpp

DLL void DoWork(ProgressCallback progressCallback)
{
        // do the work...

        if (progressCallback)
        {
            Sleep(100);
//The data which i want to share
           
        }
       
    }
}