Seperation of Interface and Implementation

Hi,

What I am trying to do is to create two dlls one with the interface and one with the implementation

1: Create an Interface in a DLL
2: Create an implementation in a seperate DLL
3: Use this in a client exe

This is what I have

1: Interface
using System ;
using System.Data ;

namespace ICTLDatabase
{
      public interface IDatabase
      {
            DataTable ExecuteSQLQuery(string sConnection, string sSQLQuery) ;
      }
}

2: Implementation
References the Interface
using System ;
using System.Data ;
using System.Data.SqlClient ;
using System.Diagnostics ;
using ICTLDatabase ;

namespace CTLDatabase
{
      public class cSQLDatabase : IDatabase
      {
      private SqlConnection m_oconn = null ;
      private SqlCommand m_cmd = null ;
      private SqlTransaction m_trans ;
      
      public cSQLDatabase()
      {
            m_cmd = new SqlCommand() ;
      }

      DataTable IDatabase.ExecuteSQLQuery(string sConnection, string sSQLQuery)
      {
            // using guarantees that Dispose is called on m_oconn, which will close the connection.
            using (m_oconn = new SqlConnection(sConnection))
            {
                  // Set the Command propeties.
                  m_cmd.CommandText = sSQLQuery ;
                  m_cmd.Connection = m_oconn ;
                  m_cmd.CommandType = CommandType.Text ;
                  SqlDataAdapter adapter = new SqlDataAdapter(m_cmd) ;
                  DataTable dataTable = new DataTable(sSQLQuery) ;
                  m_oconn.Open() ;

                  // Run the stored Procedure and place the results in dataTable.
                  adapter.Fill(dataTable) ;

                  return dataTable ;
            }
      }
}

            
               } // End cSQLDatabase
} // End Namespace


3: Client
Cut Down Version...
The client references both the above dll's like so
using ICTLDatabase ;
using CTLDatabase ;

cSQLDatabase oSQL = new cSQLDatabase() ;
IDatabase ISQL = oSQL ;
      
DataTable mydataTable = new DataTable("GET_HOTELS") ;
mydataTable = ISQL.ExecuteSPQuery(sConnection,"GET_HOTELS") ;
DataRow[] currRows = mydataTable.Select(null, null, DataViewRowState.CurrentRows);
...


When I compile everything goes fine but when I run the application in debug mode

I get an error telling me that the ICTLDatabase.dll could not be loaded or one of it's dependencies

Basically what I want to know is should what I am doing work and if so what can I do to make it work correctly.
If there is any other info you require just let me know.

FYI: When I take the interface and place it in the implementation dll  code block everythnig works fine..... Why???

Same as above but in one dll:

namespace ICTLDatabase
{
      public interface IDatabase
      {
            DataTable ExecuteSQLQuery(string sConnection, string sSQLQuery) ;
      }
}
using System ;
using System.Data ;
using System.Data.SqlClient ;
using System.Diagnostics ;
using ICTLDatabase ;

namespace CTLDatabase
{
      public class cSQLDatabase : IDatabase
      {
      private SqlConnection m_oconn = null ;
      private SqlCommand m_cmd = null ;
      private SqlTransaction m_trans ;
      
      public cSQLDatabase()
      {
            m_cmd = new SqlCommand() ;
      }

      DataTable IDatabase.ExecuteSQLQuery(string sConnection, string sSQLQuery)
      {
            // using guarantees that Dispose is called on m_oconn, which will close the connection.
            using (m_oconn = new SqlConnection(sConnection))
            {
                  // Set the Command propeties.
                  m_cmd.CommandText = sSQLQuery ;
                  m_cmd.Connection = m_oconn ;
                  m_cmd.CommandType = CommandType.Text ;
                  SqlDataAdapter adapter = new SqlDataAdapter(m_cmd) ;
                  DataTable dataTable = new DataTable(sSQLQuery) ;
                  m_oconn.Open() ;

                  // Run the stored Procedure and place the results in dataTable.
                  adapter.Fill(dataTable) ;

                  return dataTable ;
            }
      }
}

            
               } // End cSQLDatabase
} // End Namespace


Cheers,

DarrenStart Free Trial