在实体框架中加入左外部

Question

我正在通过连接4个表来尝试左外连接实体框架：

var ssss = (from supplier in entity.Supplier_master 
            join city in entity.City_master on supplier.Supplier_City equals city.id 
            join state in entity.State_master on supplier.Supplier_State equals state.id 
            join country in entity.Country_master on supplier.Supplier_Country equals country.id 
            where supplier.Supplier_Code.Equals(sup_code) 
            select (new { supplier.Supplier_Code, supplier.Supplier_Name, city.City_Name, state.State_Name, country.Country_Name, supplier.Supplier_TradeMark })).ToList();

上面的代码作为内部联接执行，请帮我找到完成左外连接的解决方案。