Problem in calling C++ dll from C# Code


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 :
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:
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:
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

posted on 2005-12-22 23:59  cy163  阅读(...)  评论(...编辑  收藏