我如何通过功能委托给被调用LINQ？ [英] How do I pass function delegates to be called with LINQ?

问题描述

我想我提出正确的问题在这里...

I think I'm asking the right question here...

我有一个返回相同数据的不同子集4的存储过程。

I have 4 stored procedures that return different subsets of the same data.

我映射在我的服务器应用程序这一数据同一个对象。

I map this data to the same object in my server application.

我已经把我的code，如下所示：

I've set my code up as follows:

internal static MyDataContext dc = new MyDataContext();

internal static List<MyObj> getData(DataType data)
{
    List<MyObj> obj = null;
    switch (data) 
    {
        case DataType.Type1:
            obj = mapObj(dc.getDataType1);
            break;
        case DateType.Type2:
            obj = mapObj(dc.getDataType2);
            break;
        ...
    }
}

// This gives me an error that type T cannot be defined
// private static List<MyObj> mapObj(Func<T> getDataForObj)
// This gives me an error calling the function (Cannot find implementation of query pattern for source type T
private static List<MyObj> mapObj<T>(Func<T> getDataForObj)
{
    List<MyObj> obj = new List<MyObj>();

    var result = from a in getDataForObj()
                 select a;

    foreach (var row in result)
    {
        ... // map objs 
    }    

    return obj;
}

请参阅我的意见就方法声明为我遇到的问题。我将如何做到这一点是否正确？我的目标是只是不具有相同的code复制/粘贴多次......试图遵循DRY原则。在此先感谢您的帮助。

Please see my comments regarding the method declaration for the issues I'm having. How would I accomplish this correctly? My goal was to just not have the same code copy/pasted multiple times...trying to follow DRY principles. Thanks in advance for your help.

推荐答案

让我mapObj功能如下（在评论中每@乔恩飞碟双向的建​​议），允许它来编译和运行：

Making my mapObj function as follows (Per @Jon Skeet's recommendation in the comments) allowed it to compile and run:

private static List<MyObj> mapObj<T>(Func<IEnumerable<T>> getDataForObj)
{
    List<MyObj> obj = new List<MyObj>();

    var result = from a in getDataForObj()
                 select a;

    foreach (var row in result)
    {
        ... // map objs 
    }    

    return obj;
}

这导致了有关领域的映射一个新的问题，但我会问，在一个新的问题。

This led to a new problem regarding the mapping of the fields, but I will ask that in a new question.

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