blocks|key|1096941|text|感谢@psaxton数组指出了comment和其他集合之间的区别。作为扩展方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1096942|public+static+class+TypeHelperExtensions
{
++++///+<summary>
++++///+If+the+given+<paramref+name="type"/>+is+an+array+or+some+other+collection
++++///+comprised+of+0+or+more+instances+of+a+"subtype",+get+that+type
++++///+</summary>
++++///+<param+name="type">the+source+type</param>
++++///+<returns></returns>
++++public+static+Type+GetEnumeratedType(this+Type+type)
++++{
++++++++//+provided+by+Array
++++++++var+elType+=+type.GetElementType();
++++++++if+(null+!=+elType)+return+elType;

++++++++//+otherwise+provided+by+collection
++++++++var+elTypes+=+type.GetGenericArguments();
++++++++if+(elTypes.Length+>+0)+return+elTypes[0];

++++++++//+otherwise+is+not+an+'enumerated'+type
++++++++return+null;
++++}
}|code-block|syntax|javascript|1096943|用法：|1096944|typeof(Foo).GetEnumeratedType();+//+null
typeof(Foo[]).GetEnumeratedType();+//+Foo
typeof(List<Foo>).GetEnumeratedType();+//+Foo
typeof(ICollection<Foo>).GetEnumeratedType();+//+Foo
typeof(IEnumerable<Foo>).GetEnumeratedType();+//+Foo

//+some+other+oddities
typeof(HashSet<Foo>).GetEnumeratedType();+//+Foo
typeof(Queue<Foo>).GetEnumeratedType();+//+Foo
typeof(Stack<Foo>).GetEnumeratedType();+//+Foo
typeof(Dictionary<int,+Foo>).GetEnumeratedType();+//+int
typeof(Dictionary<Foo,+int>).GetEnumeratedType();+//+Foo,+seems+to+work+against+key|1096945|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/4129850/1037948^0|F|7|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

Thanks to @psaxton <a href="https://stackoverflow.com/a/4129850/1037948">comment</a> pointing out the difference between Array and other collections. As an extension method:

<pre><code>public static class TypeHelperExtensions
{
 /// &lt;summary&gt;
 /// If the given &lt;paramref name="type"/&gt; is an array or some other collection
 /// comprised of 0 or more instances of a "subtype", get that type
 /// &lt;/summary&gt;
 /// &lt;param name="type"&gt;the source type&lt;/param&gt;
 /// &lt;returns&gt;&lt;/returns&gt;
 public static Type GetEnumeratedType(this Type type)
 {
 // provided by Array
 var elType = type.GetElementType();
 if (null != elType) return elType;

 // otherwise provided by collection
 var elTypes = type.GetGenericArguments();
 if (elTypes.Length &gt; 0) return elTypes[0];

 // otherwise is not an 'enumerated' type
 return null;
 }
}
</code></pre>

<h3>Usage:</h3>

<pre><code>typeof(Foo).GetEnumeratedType(); // null
typeof(Foo[]).GetEnumeratedType(); // Foo
typeof(List&lt;Foo&gt;).GetEnumeratedType(); // Foo
typeof(ICollection&lt;Foo&gt;).GetEnumeratedType(); // Foo
typeof(IEnumerable&lt;Foo&gt;).GetEnumeratedType(); // Foo

// some other oddities
typeof(HashSet&lt;Foo&gt;).GetEnumeratedType(); // Foo
typeof(Queue&lt;Foo&gt;).GetEnumeratedType(); // Foo
typeof(Stack&lt;Foo&gt;).GetEnumeratedType(); // Foo
typeof(Dictionary&lt;int, Foo&gt;).GetEnumeratedType(); // int
typeof(Dictionary&lt;Foo, int&gt;).GetEnumeratedType(); // Foo, seems to work against key
</code></pre>

blocks|key|1096977|text|感谢@drzaus的漂亮answer，但它可以被压缩成一个线条(加上对null和IEnumerable类型的检查)：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1096978|public+static+Type+GetEnumeratedType(this+Type+type)+=>
+++type?.GetElementType()
+++??+typeof(IEnumerable).IsAssignableFrom(type)
+++?+type.GenericTypeArguments.FirstOrDefault()
+++:+null;|code-block|syntax|javascript|1096979|添加了null检查器以避免异常，也许我不应该这样做(请随意删除Null+Conditional+Operators)。还添加了一个筛选器，以便该函数仅适用于集合，而不适用于任何泛型类型。|1096980|请记住，这也可能被实现的子类所欺骗，这些子类更改了集合的主题，而实现者决定将集合的泛型参数移到后面的位置。|1096981|1096982|C#8和可空性的转换答案：|1096983|public+static+Type+GetEnumeratedType(this+Type+type)+=>+
++++++++((type?.GetElementType()+??+(typeof(IEnumerable).IsAssignableFrom(type)
++++++++++++?+type.GenericTypeArguments.FirstOrDefault()
++++++++++++:+null))!;|1096984|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/1037948/drzaus|1|https://stackoverflow.com/a/21995826/75500|2|https://docs.microsoft.com/en-us/dotnet/articles/csharp/language-reference/operators/null-conditional-operators^0|Z|4|14|B|2|7|0|C|6|1|0|0|3|4|V|Q|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@$9|1A|A|1B|1|1C]|$9|1D|A|1E|1|1F]]|E|$]]|$1|F|3|G|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@$9|1K|A|1L|1|1M]]|E|$]]|$1|M|3|N|5|6|7|1N|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1O|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1P|8|@]|D|@]|E|$]]|$1|R|3|S|5|H|7|1Q|8|@]|D|@]|E|$I|J]]|$1|T|3|-4|5|6|7|1R|8|@]|D|@]|E|$]]]|U|$V|$5|W|X|Y|E|$Z|10]]|11|$5|W|X|Y|E|$Z|12]]|13|$5|W|X|Y|E|$Z|14]]]]

Thanks to <a href="https://stackoverflow.com/users/1037948/drzaus">@drzaus</a> for his nice <a href="https://stackoverflow.com/a/21995826/75500">answer</a>, but it can be compressed to a oneliner (plus check for <code>null</code>s and <code>IEnumerable</code> type):
<pre><code>public static Type GetEnumeratedType(this Type type) =&gt;
 type?.GetElementType()
 ?? typeof(IEnumerable).IsAssignableFrom(type)
 ? type.GenericTypeArguments.FirstOrDefault()
 : null;
</code></pre>
Added <code>null</code> checkers to avoid exception, maybe I shouldn't (feel free to remove the <a href="https://docs.microsoft.com/en-us/dotnet/articles/csharp/language-reference/operators/null-conditional-operators" rel="nofollow noreferrer">Null Conditional Operators</a>).
Also added a filter so the function only works on collections, not any generic types.
And bear in mind that this could also be fooled by implemented subclasses that change the subject of the collection and the implementor decided to move the collection's generic-type-argument to a later position.
<hr />
Converted answer for C#8 and nullability:
<pre><code>public static Type GetEnumeratedType(this Type type) =&gt; 
 ((type?.GetElementType() ?? (typeof(IEnumerable).IsAssignableFrom(type)
 ? type.GenericTypeArguments.FirstOrDefault()
 : null))!;
</code></pre>

Say I have an <code>System.String[]</code> type object. I can query the type object to determine if it is an array 

<pre><code>Type t1 = typeof(System.String[]);
bool isAnArray = t1.IsArray; // should be true
</code></pre>

However how do I get a type object of the array item from t1

<pre><code>Type t2 = ....; // should be typeof(System.String)
</code></pre>

How do I get the Array Item Type from Array Type in .net

假设我有一个System.String[]类型的对象。我可以查询类型对象来确定它是否是数组Type t1 = typeof(System.String[]);bool isAnArray = t1.IsArray; // should be true但是，如何从t1获取数组项的类型对象Type t2 = ....; /...

问如何从.net中的数组类型获取数组项类型
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