importing a an unmanged dll and calling a function in c# code from my unmanged dll passing pointrs using ref and out

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C#2.0

C#

please help me
i m importing a an unmanged dll and calling a function in c# code from my unmanged dll but i m facing error
This is my code :--

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.
InteropServices;
using System.IO;

namespace usingdifferentclasses
{
    class greeting
    {
        [DllImport(unmanaged.dll", SetLastError = true)]    // importing dll
        public static  extern int XRay_SearchDevices(out  string[][] pDeviceList, out int pDeviceCount, uint ulFlags);  //function prototype
    }

    class Program
    {
        public delegate int mydelegate(out string[][] pDeviceList, out int pDeviceCount, uint ulFlags);     //declaring delegates
        static  void Main(string[] args)
        {
           
            int a;
            string[][] array;
            greeting g = new greeting();     //creating obj of delegate
          // mydelegate d = new mydelegate(g.XRay_SearchDevices);    //(associating delegate with function)     gives error 

            mydelegate d = new mydelegate(greeting.XRay_SearchDevices);    /// (associating delegate with function)  this works
            d(out  array, out a, 0);  // function is called.
        }
    }
}

the error i get is :An unhandled exception of type 'System.Runtime.InteropServices.MarshalDirectiveException' occurred in program without initialising ourdll.exe

Additional information: Cannot marshal 'parameter #1': There is no marshaling support for nested arrays.

Thanks and Regards

Md.Aasif Eqbal Aslam.
aasifaslamy85@gmai.com
mumbai (india)