linq到sql案例查询

我在用c#中的linq to sql数据查询表达式构建查询时遇到问题。

我最终要做的是基于这个伪代码表达式。

public IQueryable<CTest> searchRecords(string category, string searchString, DateTime startDate, DateTime endDate, int searchType, int searchType2)
        {
            //-Search All Records
            //-From the information table
            //-By the category column containing a specific search
            //-Also by
            //  ~if both a startDate and endDate are entered (not (0000,00,00) OR null) then get records
            //  by this expression
            //  ~else then don't worry about this statement
            //-Also by
            //  ~if a searchType is equal zero(0) then search for records from the 
            //  search_type table equal to zero(0)
            //  ~if a searchType is equal one(1) then search for records from the 
            //  search_type table equal to one(1)
            //  ~else then don't worry about this statement
            //-Also by
            //  ~if a searchType2 is equal zero(0) then search for records from the 
            //  search_type table equal to zero(0)
            //  ~if a searchType2 is equal one(1) then search for records from the 
            //  search_type table equal to one(1)
            //  ~else then don't worry about this statement

            //Here is my attempt at it
            /*  
                var table = db.table1;

                switch (category)
                {
                case "_category1":
                    var records =
                        from c in table
                        where c.column1.ToString().Contains(searchString)
                        select new CTest
                        {
                            test_id = c.id,
                            test_name = c.name,
                            test_number = c.number,
                            date = ((startDate != null) && (endDate != null)) ? ((c.test_date >= startDate) && (c.test_date <= endDate)) :
                                         c.test_date),
                            test_type = (searchType == 0 ? (c.searchType = 0) :
                                        searchType == 1 ? (c.searchType = 1) :
                                        c.searchType),
                            test_type2 = (searchType2 == 0 ? (c.searchType2 = 0) :
                                        searchType2 == 1 ? (c.searchType2 = 1) :
                                        c.searchType2)
                        };
                    break;
                default:
                    break;
                }
             */
        }

提前谢谢。