以下是什么区别 -
CreateQuery() ExecuteFunction(), ExecuteStoreQuery() and ExecuteStoreCommand()
据我所知,CreateQuery用于Entity SQL&其余的方法用于DB中定义的sql函数或存储过程。
根据ObjectContext类元数据,它们如下:
CreateQuery():Creates an System.Data.Objects.ObjectQuery<T> in the current object context by using the specified query string.
Returned -> System.Data.Objects.ObjectQuery<T>
ExecuteFunction(): Executes a stored procedure or function that is defined in the data source and expressed in the conceptual model; discards any results returned from
the function; and returns the number of rows affected by the execution.
Returned -> The number of rows affected.
This has an overloaded version which return -> The entity type of the System.Data.Objects.ObjectResult<T>
ExecuteStoreCommand(): Executes an arbitrary command directly against the data source using the existing connection.
Return -> The number of rows affected.
ExecuteStoreQuery(): Executes a query directly against the data source that returns a sequence of typed results.
Return -> An enumeration of objects of type TResult.
根据上述信息 -
Use ExecuteFunction() if you have added db Function/Stored Procedure in your EDMX & can be used for both insert/update & getting result set.
Use ExecuteStoredCommand() if you have not added db Function/Stored Procedure in your EDMX & can be used to insert/update only.
ExecuteStoreQuery() can do what Executefuction() can do except that you no need to add your db Function/Stored Procedure in EDMX & IEnumerable can be used as return type.
如果我错了,请纠正我。任何进一步的信息将受到高度赞赏。
答案 0 :(得分:3)
与 CreateQuery 非常类似:
var id = 42;
using(var ctx = new Entities()){
var query = ctx.Companies.Where(o=>o.Id==id);
var result = query.First();
}
在我调用First()之前,查询只是一个查询。没有任何内容发送到数据库。只有在询问数据时才会执行查询并检索数据。
写lambda很容易,但是可以说你可以为了其他好处而牺牲它。如果EDMX不知道您的数据映射,您基本上只能使用 ExecuteStoreQuery 。防爆。你手动创建了映射。
var queryString = "SELECT ... FROM " + tableName;
var table = context.ExecuteStoreQuery<ResultTableTemplate>(queryString );
为您的应用程序编写代码很好,但有时数据库比几个用户界面更长。为了最大限度地减少需要完成的工作量,您可以在数据库中存储一些(如果不是全部)功能。它们可以主要存储在功能或程序中。
ExecuteFunction仅用于函数导入。函数是计算值,不能对SQL Server执行永久性环境更改(即不允许INSERT或UPDATE语句)。在C#中调用自定义函数Select Today()
:
var date = ctx.ExecuteFunction<DateTime>("Today").First();
实体框架支持三种加载相关数据的方法 - 急切加载,延迟加载和显式加载。默认情况下它是延迟加载,这就是为什么你看到我使用 .First()/ .FirstOrDefault / .ToList /...的原因,有关如何根据需要加载数据的更多信息,你可以采取看看Loading Related Entities。
程序就像数据库批处理脚本。如果您使用数据库优先设计,则很可能大多数业务逻辑将存储在过程中。你可以用c#来称呼它们:
var cmdText = "[DoStuff] @Name = @name_param, @Age = @age_param";
var @params = new[]{
new SqlParameter("name_param", "Josh"),
new SqlParameter("age_param", 45)
};
ObjectContext.ExecuteStoreQuery<MyObject>(cmdText, @params);
奖金:
您希望做的一件事是call a stored procedure that accepts a table value parameter。