using System;
using Gtk;
using Mono.Data.Sqlite;
using System.Data;

namespace BB
{
    public partial class BBLogin : Gtk.Window
    {
        public BBLogin () :
            base (Gtk.WindowType.Toplevel)
        {
            this.Build ();
        }

        private void btnLoginOnClick (object sender, EventArgs e)
        {
            SqliteConnection conn = new SqliteConnection();
            conn.ConnectionString = "Data Source=BBUser.sqlite;Version=3;";
            SqliteCommand command = new SqliteCommand();
            command.CommandText = ("SELECT UserName FROM T_test WHERE UserName=@UserName AND Password=@Password");
            command.Parameters.AddWithValue ("@UserName", txtUserName.Text);
            command.Parameters.AddWithValue ("@Password", txtPassword.Text);

            conn.Open ();
            SqliteConnection.CreateFile("failsafe0.sqlite");
            object result = command.ExecuteScalar();
            SqliteConnection.CreateFile("failsafe1.sqlite");
            conn.Close ();
            SqliteConnection.CreateFile("failsafe2.sqlite");
            string userNameLogin = Convert.ToString(result);
            SqliteConnection.CreateFile("failsafe3.sqlite");

            if (userNameLogin != "")
            {
                SqliteConnection.CreateFile("success.sqlite");
                /*MessageDialog md = new MessageDialog ("Username was correct!");
                md.Run ();
                md.Destroy();*/
            }
            else
            {
                SqliteConnection.CreateFile("failed.sqlite");
                /*MessageDialog md = new MessageDialog ("Username or password is incorrect!");
                md.Run ();
                md.Destroy();*/
            }
        }

    }
}

Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidOperationException: No connection associated with this command
  at Mono.Data.Sqlite.SqliteCommand.InitializeForReader () [0x00000] in <filename unknown>:0
  at Mono.Data.Sqlite.SqliteCommand.ExecuteReader (CommandBehavior behavior) [0x00000] in <filename unknown>:0
  at Mono.Data.Sqlite.SqliteCommand.ExecuteScalar () [0x00000] in <filename unknown>:0
  at BB.BBLogin.btnLoginOnClick (System.Object sender, System.EventArgs e) [0x0006c] in /home/christian/BB/BB/BBLogin.cs:27
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  --- End of inner exception stack trace ---
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <filename unknown>:0
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000] in <filename unknown>:0
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)
   at Gtk.Application.gtk_main()
   at Gtk.Application.Run()
   at BB.MainClass.Main(System.String[] args) in /home/christian/BB/BB  /Program.cs:line 15