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.