c# – 在Entity Framework下了解多个表结果

2019年8月3日 129次阅读

为了显示一个页面,我需要从各种表中获取大量信息,而现在,加载页面大约需要20秒,这太可怕了.

所以我想将所有内容都移到一个Store Procedure中,并以旧的DataTable方式获取所有信息.

我明白了

public WinnerPageInformation FindWinnerPageInformation(int calendarId)
{
    BackendPagesContext ctx = new BackendPagesContext(db.Connection);
    IMultipleResults results = ctx.WinnersBackendPageInformation(calendarId);

    return new WinnerPageInformation()
    {
        Challenges = results.GetResult<Challenges>(),
        Content = results.GetResult<ContentWinners>().FirstOrDefault(),
        Einfo = results.GetResult<ContentEmails>().FirstOrDefault(),
        Fields = results.GetResult<SubscriberFields>(),
        Prizes = results.GetResult<Prizes>(),
        Winners = results.GetResult<Winners>()
    };
}

和WinnersBackendPageInformation看起来像这样

public class BackendPagesContext : DataContext
{
    public BackendPagesContext(System.Data.IDbConnection connection) 
        : base(connection) { }

    [Function(Name = "dbo.sp_GetWinnersBackendPageInformation")]
    [ResultType(typeof(JK_ContentWinners))]
    [ResultType(typeof(JK_Winners))]
    [ResultType(typeof(JK_SubscriberFields))]
    [ResultType(typeof(JK_Prizes))]
    [ResultType(typeof(JK_Challenges))]
    [ResultType(typeof(JK_ContentEmails))]
    public IMultipleResults WinnersBackendPageInformation(
        [Parameter(Name = "calendarId", DbType = "Int")] int calendarId)
    {
        IExecuteResult result =
        this.ExecuteMethodCall(this,
                               ((MethodInfo)(MethodInfo.GetCurrentMethod())),
                               calendarId);
        return (IMultipleResults)(result.ReturnValue);
    }
}

public interface IMultipleResults : IFunctionResult, IDisposable
{
    IEnumerable<TElement> GetResult<TElement>();
}

但我遇到的问题是,行.ExecuteMethodCall抛出一个错误,说结果不是MultipleTable结果.

我的商店程序看起来像

ALTER PROCEDURE sp_GetWinnersBackendPageInformation
    @calendarId numeric = 0
AS
BEGIN 
    SELECT * FROM ContentWinners WHERE calendar_id = @calendarId;
    SELECT * FROM Winners WHERE calendar_id = @calendarId;
    SELECT * FROM SubscriberFields WHERE calendar_id = @calendarId ORDER BY position;
    SELECT * FROM Prizes WHERE calendar_id = @calendarId ORDER BY prizetype_id, to_day, title;
    SELECT * FROM Challenges WHERE calendar_id = @calendarId;
    SELECT * FROM ContentEmails WHERE calendar_id = @calendarId;
END
GO

错误信息是

More than one result type declared for function ‘WinnersBackendPageInformation’ that does not return IMultipleResults.

我错过了什么？

最佳答案 你没有遗漏任何东西.

实体框架4不支持存储过程中的多个结果集.

如果您阅读博客文章here,您将从EF团队成员那里找到此声明：

Unfortunately we weren’t able to get full support for multiple results into the product this time around. We did, however, add the method Translate<T> to ObjectContext which allows you to materialize objects from a DataReader. So if you have a stored procedure which returns multiple results whose properties directly align with EF objects, then you could get the underlying store connection from the context (context.Connection.StoreConnection), create a command and use it to execute the stored procedure and get back the DataReader. Then you could call Translate<FirstObjectType> and get back an enumerable of those objects, followed by reader.NextResult() and Translate<SecondObjectType>, etc.

所以,你可以使用一些“老派”ADO.NET,或者你也可以试试CodePlex上的EF Extensions项目,它似乎可以为你做管道工作.

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