blocks|key|1476108|text|为什么不创建一个类来封装结果呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1476109|public+class+Result
{
+++++public+IList<Foo>+List+{+get;+set;+}
+++++public+Int32+Count+{+get;+set;+}
}|code-block|syntax|javascript|1476110|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Why not create a class to encapsulate the results?

<pre><code>public class Result
{
 public IList&lt;Foo&gt; List { get; set; }
 public Int32 Count { get; set; }
}
</code></pre>

blocks|key|1476187|text|你可以把它包装在一个lambda/delegate/function/方法中，这个方法公开了正确的接口并调用了FindForBar，但是我怀疑FindForBar会将其作为输出参数，所以你需要确保丢弃这个信息是可以的/安全的/可取的/有正确的结果(即使你可以直接传入FindForBar，你也需要确保这一点)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1476188|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You could wrap it in a lambda/delegate/function/method that exposed the right interface and called FindForBar, but I suspect that FindForBar has count as an out parameter as a reason, so you'd need to be sure throwing that information away was ok/safe/desirable/had the right results (you'd need to be sure of this even if you could just directly pass in FindForBar).

blocks|key|1261673|text|ref和out不是类型参数定义的一部分，因此不能使用内置的Func委托来传递ref和out参数。当然，如果你愿意，你可以声明你自己的委托：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1261674|delegate+V+MyDelegate<T,U,V>(T+input,+out+U+output);|code-block|syntax|javascript|1261675|entityMap^0|0|3|4|3|T|4|12|3|16|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|L|$]]

<code>ref</code> and <code>out</code> are not part of the type parameter definition so you can't use the built-in <code>Func</code> delegate to pass <code>ref</code> and <code>out</code> arguments. Of course, you can declare your own delegate if you want:

<pre><code>delegate V MyDelegate&lt;T,U,V&gt;(T input, out U output);
</code></pre>

blocks|key|1476292|text|Func委托家族(或Action+)只是简单的委托类型，声明如下|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1476293|//.NET+4+and+above
public+delegate+TResult+Func<out+TResult>()
public+delegate+TResult+Func<in+T,+out+TResult>(T+obj)

//.NET+3.5
public+delegate+TResult+Func<T1,+T2,+TResult>(T1+obj1,+T2+obj2)
public+delegate+TResult+Func<T1,+T2,+T3,+TResult>(T1+obj1,+T2+obj2,+T3+obj3)|code-block|syntax|javascript|1476294|这样的委托可以有out/ref参数，所以在你的例子中，正如其他答案所指出的那样，这只是你自己定制实现的问题。至于为什么微软没有在默认情况下打包它，想想它需要的组合的数量。|1476295|delegate+TResult+Func<T1,+T2,+TResult>(T1+obj1,+T2+obj2)
delegate+TResult+Func<T1,+T2,+TResult>(out+T1+obj1,+T2+obj2)
delegate+TResult+Func<T1,+T2,+TResult>(T1+obj1,+out+T2+obj2)
delegate+TResult+Func<T1,+T2,+TResult>(out+T1+obj1,+out+T2+obj2)|1476296|只有两个参数。我们甚至还没有接触到ref。这实际上会给开发人员带来麻烦和困惑。|1476297|entityMap^0|0|4|A|6|0|0|0|0|H|3|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

The <code>Func</code> family of delegates (or <code>Action</code> for that matter) are nothing but simple delegate types declared like

<pre><code>//.NET 4 and above
public delegate TResult Func&lt;out TResult&gt;()
public delegate TResult Func&lt;in T, out TResult&gt;(T obj)

//.NET 3.5
public delegate TResult Func&lt;T1, T2, TResult&gt;(T1 obj1, T2 obj2)
public delegate TResult Func&lt;T1, T2, T3, TResult&gt;(T1 obj1, T2 obj2, T3 obj3)
</code></pre>

etc. Delegates as such can have out/ref parameters, so in your case its only a matter of custom implementation by yourself as other answers have pointed out. As to why Microsoft did not pack this by default, think of the sheer number of combinations it would require. 

<pre><code>delegate TResult Func&lt;T1, T2, TResult&gt;(T1 obj1, T2 obj2)
delegate TResult Func&lt;T1, T2, TResult&gt;(out T1 obj1, T2 obj2)
delegate TResult Func&lt;T1, T2, TResult&gt;(T1 obj1, out T2 obj2)
delegate TResult Func&lt;T1, T2, TResult&gt;(out T1 obj1, out T2 obj2)
</code></pre>

for just two parameters. We have not even touched <code>ref</code>. It would actually be cumbersome and confusing for developers.

Can I pass a method with an out parameter as a Func?

<pre><code>public IList&lt;Foo&gt; FindForBar(string bar, out int count) { }

// somewhere else
public IList&lt;T&gt; Find(Func&lt;string, int, List&lt;T&gt;&gt; listFunction) { }
</code></pre>

Func needs a type so out won't compile there, and calling listFunction requires an int and won't allow an out in.

Is there a way to do this?

Func<T> with out parameter

我可以将带有out参数的方法作为Func传递吗？public IList<Foo> FindForBar(string bar, out int count) { }// somewhere elsepublic IList<T> Find(Func<string, int, List<T>> listFunction...

问不带out参数的Func<T>
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