Breaking Query On Basis Of Conditions

 On a webpage, there are filters to choose from. Like date, amount, SSN (multiple filters can be choosen).
I have a single query so far.
   SqlCommand cmd = new SqlCommand("SELECT [column1], [column2], [column3],  [column4], [column5] FROM [table] WHERE [column4] = 'condition4'  AND [column5] = @total_bill AND [last_change] >= @txtStartDate AND [last_change] <= @txtEndDate  ", Conn) ;


          cmd.Parameters.Add(new SqlParameter("@total_bill", total_bill1.Text));

         cmd.Parameters.Add(new SqlParameter("@txtStartDate", txtStartDate.Text));
 
         cmd.Parameters.Add(new SqlParameter("@txtEndDate", txtEndDate.Text));
 
 I want to break the query so that it executes on the basis of different sets of conditions (filters). If I dont select date filter, then the above query will not execute properly.
Please help.