扩展/方法中的 C# Linq

发布于 2024-10-31 15:38:41 字数 393 浏览 1 评论 0原文

您好，

我正在寻找创建一个包括 linq 查询的扩展方法。我正在寻找的是一种方法或扩展方法，可以执行类似这样的操作

var orderedList = OrderThisList<ModelName>(List<T> sourceList, //and something like m=>m.Username);

，其中 ModelName 是实体，Username 是我想要订购的字段。该方法看起来像

public List<T> OrderThisList<T>(//some linq property?)
{
    //What code goes here?
}

原文

Greetings

I'm looking for creating a extension method including a linq query.
What i'm looking for is either a method or extension method which can do something like this

var orderedList = OrderThisList<ModelName>(List<T> sourceList, //and something like m=>m.Username);

Where ModelName is the entity and Username is the field of which I want to order.
The method would look something like

public List<T> OrderThisList<T>(//some linq property?)
{
    //What code goes here?
}

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就此别过 2024-11-07 15:38:41

编辑：目前还非常不清楚这个问题的全部内容，但听起来我们正在处理内存中的集合而不是 LINQ to SQL 等。

如果使用 OrderBy< 的问题/code> 的缺点是它不会就地对列表进行排序，您应该使用 List.Sort()，可能会传入自定义比较器。

我的 MiscUtil 项目有一些可以帮助您的帮助程序类型。例如：

var comparison = ProjectionComparer<ModelType>.Create(m => m.SomeProperty)
                                              .ThenBy(m => m.SomeOtherProperty);
list.Sort(comparison);

如果您使用 LINQ to SQL 并且有数据上下文，您可以使用：

public List<TSource, TKey> OrderThisList<TSource, TKey>(
    Expression<Func<TSource, TKey>> ordering)
{
    return dataContext.GetTable<TSource>()
                      .OrderBy(ordering)
                      .ToList();
}

现在显然需要两个类型参数，而您只想指定一个。有多种方法可以解决这个问题 - 基本上，您希望最终得到一个泛型类型和一个带有可以推断的一个类型参数（TKey）的方法。例如：

var list = Orderer<ModelType>.Create(dataContext)
                             .OrderThisList(m => m.SomeProperty);

虽然考虑到 OrderBy 已经可用，但它有点绕房子...您能解释一下为什么需要这个，以及涉及什么 LINQ 提供程序吗？

EDIT: It's still extremely unclear what this question is all about, but it sounds like we're dealing with in-memory collections rather than LINQ to SQL etc.

If the problem with using OrderBy is that it doesn't sort the list in-place, you should be using List<T>.Sort(), possibly passing in a custom comparator.

My MiscUtil project has a few helper types which may help you. For example:

var comparison = ProjectionComparer<ModelType>.Create(m => m.SomeProperty)
                                              .ThenBy(m => m.SomeOtherProperty);
list.Sort(comparison);

If you're using LINQ to SQL and you've got a data context, you could use:

public List<TSource, TKey> OrderThisList<TSource, TKey>(
    Expression<Func<TSource, TKey>> ordering)
{
    return dataContext.GetTable<TSource>()
                      .OrderBy(ordering)
                      .ToList();
}

Now obviously that requires two type arguments, and you only want to specify one. There are various ways round this - basically you'd want to end up with a generic type and a method with one type argument (TKey) which can be inferred. For example:

var list = Orderer<ModelType>.Create(dataContext)
                             .OrderThisList(m => m.SomeProperty);

It's somewhat round-the-houses though considering that OrderBy is already available... could you explain why you want this, and also what LINQ provider is involved?

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