C# 从 IGrouping 中选择不同的值

发布于 2024-07-14 14:53:55 字数 406 浏览 3 评论 0原文

我有两个类：

class Foo 
{ 
    public Bar SomeBar { get; set; } 
}

class Bar
{ 
    public string Name { get; set; } 
}

我有一个将 Foos 分组在一起的列表：

var someGroup = from f in fooList
                orderby f.SomeBar.Name ascending
                group f by f.SomeBar.Name into Group
                select Group;

如何从 someGroup 中获取不同 Bars 的列表？

原文

I have two classes:

class Foo 
{ 
    public Bar SomeBar { get; set; } 
}

class Bar
{ 
    public string Name { get; set; } 
}

I have a list of Foos that I group together:

var someGroup = from f in fooList
                orderby f.SomeBar.Name ascending
                group f by f.SomeBar.Name into Group
                select Group;

How can I get the list of the distinct Bars from someGroup?

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记忆里有你的影子 2024-07-21 14:53:55

是否可能会有多个同名酒吧？如果是这样，那就麻烦了。如果没有，您可以将其更改为：

var grouped = from f in fooList
              orderby f.SomeBar.Name ascending
              group f by f.SomeBar into Group
              select Group;

var bars = grouped.Select(group => group.Key);

或者，如果您只想要每个 name 一个 Bar，您可以坚持原来的查询，但更改最后一位：

var someGroup = from f in fooList
                orderby f.SomeBar.Name ascending
                group f by f.SomeBar.Name into Group
                select Group;

var bars = someGroup.Select(group => group.First().SomeBar);

这将采用每个中的第一个 Foo组，并找到其 Bar。

Will there potentially be more than one Bar with the same name? If so, it's tricky. If not, you could just change it to:

var grouped = from f in fooList
              orderby f.SomeBar.Name ascending
              group f by f.SomeBar into Group
              select Group;

var bars = grouped.Select(group => group.Key);

Alternatively, if you only want one Bar per name, you could stick with your original query, but change the last bit:

var someGroup = from f in fooList
                orderby f.SomeBar.Name ascending
                group f by f.SomeBar.Name into Group
                select Group;

var bars = someGroup.Select(group => group.First().SomeBar);

This will take the first Foo in each group, and find its Bar.

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暖心男生 2024-07-21 14:53:55

如果您通过 Bar 的特殊 Equals 实现来定义“不同”，则可以使用：

var result = someGroup.SelectMany(x => x.Select(t => t.SomeBar)).Distinct();

If you define "being distinct" by a special Equals implementation for Bar, you could use:

var result = someGroup.SelectMany(x => x.Select(t => t.SomeBar)).Distinct();

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半世蒼涼 2024-07-21 14:53:55

以前有人问过类似的问题，所以我结合大家的知识做了这个：

var newlist<T2> = oldlist<T1>.GroupBy(g => g.distinct_var).Select(g => g.First()) //a
                 .Select(r=> new T2() {var1=r.va1, var2=r.var2 ...etc}).ToList(); //b

它的作用是：

a。第一行选择您选择的不同项目，这就是您想要的。

b. 第二行通过构造新的 T2 列表将旧 type1 转换为新 type2。

也许你的问题有点过分了，直接删掉你不需要的东西吧。

People asked similar questions before, So I have made this combining everyone's knowledge:

var newlist<T2> = oldlist<T1>.GroupBy(g => g.distinct_var).Select(g => g.First()) //a
                 .Select(r=> new T2() {var1=r.va1, var2=r.var2 ...etc}).ToList(); //b

What it does is:

a. First line selects distinct items of your choice, which is what you wanted.

b. Second line converts old type1 to new type2 by constructing new T2 list.

Maybe overkilled for your question, just chop out things you don't need.

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