Problem in calling C++ dll from C# Code

Hi!

I am calling a C++ dll function from my C# code . but facing the problem in a function called inside that C++ function.

That's how I'm referring to the C++ dll function inside my C# class :

Code:

   
     

      
    

class TestInterop

{


    
      [DllImport("DBApi.dll", EntryPoint="DeleteRecFromDB", ExactSpelling=false,SetLastError=true, CharSet=CharSet.Unicode)] internal extern static int DeleteRecFromDB([MarshalAs(UnmanagedType.LPWStr)]string empName,[MarshalAs(UnmanagedType.LPWStr)]string deptName);

public  TestInterop(){}



static void Main(string[] args)

{

   
    
      TestInterop.DeleteRecFromDB("KT","Dep-01");

}



}
   
     

Now my C++ function is written in DBApi.cpp as:

Code:

   
     



    
      DBApiReturns DeleteRecFromDB(CString empID, CString depName){

try

{

int returns;

         //check for required field

		if ( 
    
      CheckRequiredField(empID) == FALSE  )

            return MissingRequiredField;

		if ( CheckRequiredField(depName) == FALSE )

             return MissingRequiredField;

				


    
      pServerInterface->DeleteRec(CComBSTR(empID),CComBSTR(depName),&returns); 

			

	        if( returns != 1) 

		return (Success);

                        else

                                return(Failure);

	}

	catch(_com_error &ce)

	    {

                	return COMError ;

	     }

	     catch(...)

	    {

           	          return UnknownError ;

                     }



}
   
     

When I call this function , I get 'UnknownError' on the function CheckRequiredField().If I bypass this function the code works fine.CheckRequiredField() is define as following:

Code:

   
     

      
    

CheckRequiredField(CString field)

{

if ( field.GetLength() <= 0) return FALSE;

	return TRUE;

}
   
     

I suspect that there must be some problem in the way I'm doing the parameter marshalling.

Please Help.

thanks and regards
KT.