Entity SQL与LINQ TO Entity的本质区别

由此能够看出其最终都转移成Command Tree 而后再转换成对应数据库的T-SQL语句，本质差异不大，可是有时执行特殊查询语句的时候仍是有点不同的，由于Entity SQL的T-SQL语句是咱们本身定义的，而LINQ to Entity最后转换的T-SQL语句是由Entity引擎转换的，有时咱们用SQL Server Profiler检测执行的SQL语句的时候LINQ to Entity执行的SQL每每让咱们不容易理解，因此在须要对某些查询/修改/更新执行操做的时候若是发现执行效率不高的话能够考虑使用Entity SQL自定义执行SQL语句，下边贴出点代码：

1.LINQ TO Entity

string city = "London";
using (Entities entities = new Entities())
{
var query = from c in entities.Customers
where c.Address.City == city
select c;
foreach (Customers c in query)
     Console.WriteLine(c.CompanyName);
}

2.Entity SQL（注意SQL语句哦）

string city = "London";
using (Entities entities = new Entities())
{
     ObjectQuery<Customers> query = entities.CreateQuery<Customers>(
         "SELECT VALUE c FROM Customers AS c WHERE c.Address.City = @city",new ObjectParameter("city", city)
);
foreach (Customers c in query)
     Console.WriteLine(c.CompanyName);
}