search query in entity framework 3.5

I need to build a search query on Customers table join with orders table

string firstname  = "Joe";
 string emailFilter = "joe@email.com";
 string city=null;

In SQL we can make 开发者_开发技巧like this

SELECT @sql =                                                       
    'SELECT  * from  
     FROM   dbo.Orders o                                     
     inner join
     JOIN   dbo.Customers c ON o.CustomerID = c.CustomerID      
        WHERE  1 = 1'       

IF @firstname IS NOT NULL                                             
   SELECT @sql = @sql + ' AND c.firstname= @firstname'          


IF @city IS NOT NULL                                         
   SELECT @sql = @sql + ' AND c.city >= @city'

I need to build a entity framework 3.5 linq query joined with orders and customers table with dynamic search condition.

if the values are not null, i need to use in where clause in linq

I am new to Linq. shall we need to use Iqueryable. Any help appreciated.

Thanks

You can try something like :

var result = from o in context.Orders.include("customers")
             where o.city == (city == null ? o.city : city) && o.firstname == (firstname == null ? o.firstname : firstname)
             select o;

You can check Dynamic Linq here http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx it will help you or search stackoverflow.com for dynamic-linq tag questions and answers https://stackoverflow.com/questions/tagged/dynamic-linq