blocks|key|1548471|text|typeof(IEnumerable<Foo>).GetGenericArguments()[0]将返回第一个泛型参数-在本例中为typeof(Foo)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1548472|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.type.getgenericarguments.aspx^0|0|O|P|O|1T|B|P|L|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

<code>typeof(IEnumerable&lt;Foo&gt;)</code>.<a href="http://msdn.microsoft.com/en-us/library/system.type.getgenericarguments.aspx" rel="nofollow noreferrer"><code>GetGenericArguments()</code></a><code>[0]</code> will return the first generic argument - in this case <code>typeof(Foo)</code>.

blocks|key|1548528|text|如果你知道IEnumerable<T>+(通过泛型)，那么只需要typeof(T)就可以了。否则(对于object或非通用IEnumerable)，请检查实现的接口：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1548529|++++++++object+obj+=+new+string[]+{+"abc",+"def"+};
++++++++Type+type+=+null;
++++++++foreach+(Type+iType+in+obj.GetType().GetInterfaces())
++++++++{
++++++++++++if+(iType.IsGenericType+&&+iType.GetGenericTypeDefinition()
++++++++++++++++==+typeof(IEnumerable<>))
++++++++++++{
++++++++++++++++type+=+iType.GetGenericArguments()[0];
++++++++++++++++break;
++++++++++++}
++++++++}
++++++++if+(type+!=+null)+Console.WriteLine(type);|code-block|syntax|javascript|1548530|entityMap^0|5|E|W|9|1F|6|1P|B|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]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|L|$]]

If you know the <code>IEnumerable&lt;T&gt;</code> (via generics), then just <code>typeof(T)</code> should work. Otherwise (for <code>object</code>, or the non-generic <code>IEnumerable</code>), check the interfaces implemented:

<pre><code> object obj = new string[] { "abc", "def" };
 Type type = null;
 foreach (Type iType in obj.GetType().GetInterfaces())
 {
 if (iType.IsGenericType &amp;&amp; iType.GetGenericTypeDefinition()
 == typeof(IEnumerable&lt;&gt;))
 {
 type = iType.GetGenericArguments()[0];
 break;
 }
 }
 if (type != null) Console.WriteLine(type);
</code></pre>

blocks|key|1333184|text|非常感谢您的讨论。我使用它作为下面解决方案的基础，它适用于我感兴趣的所有情况(IEnumerable、派生类等)。我想我应该在这里分享一下，以防有人也需要它：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1333185|++Type+GetItemType(object+someCollection)
++{
++++var+type+=+someCollection.GetType();
++++var+ienum+=+type.GetInterface(typeof(IEnumerable<>).Name);
++++return+ienum+!=+null
++++++?+ienum.GetGenericArguments()[0]
++++++:+null;
++}|code-block|syntax|javascript|1333186|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|$]]

Thank you very much for the discussion. I used it as a basis for the solution below, which works well for all cases that are of interest to me (IEnumerable, derived classes, etc). Thought I should share here in case anyone needs it also:

<pre><code> Type GetItemType(object someCollection)
 {
 var type = someCollection.GetType();
 var ienum = type.GetInterface(typeof(IEnumerable&lt;&gt;).Name);
 return ienum != null
 ? ienum.GetGenericArguments()[0]
 : null;
 }
</code></pre>

blocks|key|1548601|text|我只需要做一个扩展方法。这对我所做的一切都很有效。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1548602|public+static+Type+GetItemType<T>(this+IEnumerable<T>+enumerable)
{
++++return+typeof(T);
}|code-block|syntax|javascript|1548603|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|$]]

I'd just make an extension method. This worked with everything I threw at it. 

<pre><code>public static Type GetItemType&lt;T&gt;(this IEnumerable&lt;T&gt; enumerable)
{
 return typeof(T);
}
</code></pre>

blocks|key|1333265|text|对于更简单的情况，当它是IEnumerable<T>或T时，注意使用GenericTypeArguments而不是GetGenericArguments()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1333266|Type+inputType+=+o.GetType();
Type+genericType;
if+((inputType.Name.StartsWith("IEnumerable"))
++++&&+((genericType+=+inputType.GenericTypeArguments.FirstOrDefault())+!=+null))+{

++++return+genericType;
}+else+{
++++return+inputType;
}|code-block|syntax|javascript|1333267|entityMap^0|C|E|R|1|Y|K|1L|L|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]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|L|$]]

An alternative for simpler situations where it's either going to be an <code>IEnumerable&lt;T&gt;</code> or <code>T</code> - note use of <code>GenericTypeArguments</code> instead of <code>GetGenericArguments()</code>.

<pre><code>Type inputType = o.GetType();
Type genericType;
if ((inputType.Name.StartsWith("IEnumerable"))
 &amp;&amp; ((genericType = inputType.GenericTypeArguments.FirstOrDefault()) != null)) {

 return genericType;
} else {
 return inputType;
}
</code></pre>

blocks|key|1333306|text|我也遇到过类似的问题。选择的答案适用于实际情况。在我的例子中，我只有一个类型(来自PropertyInfo)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1333307|当类型本身是typeof(IEnumerable<T>)而不是IEnumerable<T>的实现时，选择的答案将失败。|1333308|在这种情况下，以下方法有效：|1333309|public+static+Type+GetAnyElementType(Type+type)
{
+++//+Type+is+Array
+++//+short-circuit+if+you+expect+lots+of+arrays+
+++if+(type.IsArray)
++++++return+type.GetElementType();

+++//+type+is+IEnumerable<T>;
+++if+(type.IsGenericType+&&+type.GetGenericTypeDefinition()+==+typeof+(IEnumerable<>))
++++++return+type.GetGenericArguments()[0];

+++//+type+implements/extends+IEnumerable<T>;
+++var+enumType+=+type.GetInterfaces()
+++++++++++++++++++++++++++.Where(t+=>+t.IsGenericType+&&+
++++++++++++++++++++++++++++++++++t.GetGenericTypeDefinition()+==+typeof(IEnumerable<>))
+++++++++++++++++++++++++++.Select(t+=>+t.GenericTypeArguments[0]).FirstOrDefault();
+++return+enumType+??+type;
}|code-block|syntax|javascript|1333310|entityMap^0|15|C|0|6|M|V|E|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Y|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|Z|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

I had a similar problem. The selected answer works for actual instances.
In my case I had only a type (from a <code>PropertyInfo</code>).

The selected answer fails when the type itself is <code>typeof(IEnumerable&lt;T&gt;)</code> not an implementation of <code>IEnumerable&lt;T&gt;</code>.

For this case the following works:

<pre><code>public static Type GetAnyElementType(Type type)
{
 // Type is Array
 // short-circuit if you expect lots of arrays 
 if (type.IsArray)
 return type.GetElementType();

 // type is IEnumerable&lt;T&gt;;
 if (type.IsGenericType &amp;&amp; type.GetGenericTypeDefinition() == typeof (IEnumerable&lt;&gt;))
 return type.GetGenericArguments()[0];

 // type implements/extends IEnumerable&lt;T&gt;;
 var enumType = type.GetInterfaces()
 .Where(t =&gt; t.IsGenericType &amp;&amp; 
 t.GetGenericTypeDefinition() == typeof(IEnumerable&lt;&gt;))
 .Select(t =&gt; t.GenericTypeArguments[0]).FirstOrDefault();
 return enumType ?? type;
}
</code></pre>

blocks|key|1333363|text|这是对Eli+Algranti的解决方案的改进，因为它还可以在继承树中IEnumerable<>类型处于任何级别的情况下工作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1333364|此解决方案将从任何Type获取元素类型。如果类型不是IEnumerable<>，它将返回传入的类型。对于对象，请使用GetType。对于类型，使用typeof，然后对结果调用此扩展方法。|1333365|public+static+Type+GetGenericElementType(this+Type+type)
{
++++//+Short-circuit+for+Array+types
++++if+(typeof(Array).IsAssignableFrom(type))
++++{
++++++++return+type.GetElementType();
++++}

++++while+(true)
++++{
++++++++//+Type+is+IEnumerable<T>
++++++++if+(type.IsGenericType+&&+type.GetGenericTypeDefinition()+==+typeof(IEnumerable<>))
++++++++{
++++++++++++return+type.GetGenericArguments().First();
++++++++}

++++++++//+Type+implements/extends+IEnumerable<T>
++++++++Type+elementType+=+(from+subType+in+type.GetInterfaces()
++++++++++++let+retType+=+subType.GetGenericElementType()
++++++++++++where+retType+!=+subType
++++++++++++select+retType).FirstOrDefault();

++++++++if+(elementType+!=+null)
++++++++{
++++++++++++return+elementType;
++++++++}

++++++++if+(type.BaseType+==+null)
++++++++{
++++++++++++return+type;
++++++++}

++++++++type+=+type.BaseType;
++++}
}|code-block|syntax|javascript|1333366|entityMap^0|Z|D|0|9|4|Q|D|1M|7|21|6|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|N|$]]

This is an improvement on Eli Algranti's solution in that it will also work where the <code>IEnumerable&lt;&gt;</code> type is at any level in the inheritance tree.

This solution will obtain the element type from any <code>Type</code>. If the type is not an <code>IEnumerable&lt;&gt;</code>, it will return the type passed in. For objects, use <code>GetType</code>. For types, use <code>typeof</code>, then call this extension method on the result.

<pre><code>public static Type GetGenericElementType(this Type type)
{
 // Short-circuit for Array types
 if (typeof(Array).IsAssignableFrom(type))
 {
 return type.GetElementType();
 }

 while (true)
 {
 // Type is IEnumerable&lt;T&gt;
 if (type.IsGenericType &amp;&amp; type.GetGenericTypeDefinition() == typeof(IEnumerable&lt;&gt;))
 {
 return type.GetGenericArguments().First();
 }

 // Type implements/extends IEnumerable&lt;T&gt;
 Type elementType = (from subType in type.GetInterfaces()
 let retType = subType.GetGenericElementType()
 where retType != subType
 select retType).FirstOrDefault();

 if (elementType != null)
 {
 return elementType;
 }

 if (type.BaseType == null)
 {
 return type;
 }

 type = type.BaseType;
 }
}
</code></pre>

blocks|key|1548790|text|我通常是这样做的(通过扩展方法)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1548791|public+static+Type+GetIEnumerableUnderlyingType<T>(this+T+iEnumerable)
++++{
++++++++return+typeof(T).GetTypeInfo().GetGenericArguments()[(typeof(T)).GetTypeInfo().GetGenericArguments().Length+-+1];
++++}|code-block|syntax|javascript|1548792|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|$]]

this is how I usually do it (via extension method):

<pre><code>public static Type GetIEnumerableUnderlyingType&lt;T&gt;(this T iEnumerable)
 {
 return typeof(T).GetTypeInfo().GetGenericArguments()[(typeof(T)).GetTypeInfo().GetGenericArguments().Length - 1];
 }
</code></pre>

blocks|key|1333416|text|我知道这有点老了，但我相信这个方法会涵盖评论中提到的所有问题和挑战。感谢Eli+Algranti启发了我的工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1333417|///+<summary>Finds+the+type+of+the+element+of+a+type.+Returns+null+if+this+type+does+not+enumerate.</summary>
///+<param+name="type">The+type+to+check.</param>
///+<returns>The+element+type,+if+found;+otherwise,+<see+langword="null"/>.</returns>
public+static+Type+FindElementType(this+Type+type)
{
+++if+(type.IsArray)
++++++return+type.GetElementType();

+++//+type+is+IEnumerable<T>;
+++if+(ImplIEnumT(type))
++++++return+type.GetGenericArguments().First();

+++//+type+implements/extends+IEnumerable<T>;
+++var+enumType+=+type.GetInterfaces().Where(ImplIEnumT).Select(t+=>+t.GetGenericArguments().First()).FirstOrDefault();
+++if+(enumType+!=+null)
++++++return+enumType;

+++//+type+is+IEnumerable
+++if+(IsIEnum(type)+%7C%7C+type.GetInterfaces().Any(IsIEnum))
++++++return+typeof(object);

+++return+null;

+++bool+IsIEnum(Type+t)+=>+t+==+typeof(System.Collections.IEnumerable);
+++bool+ImplIEnumT(Type+t)+=>+t.IsGenericType+&&+t.GetGenericTypeDefinition()+==+typeof(IEnumerable<>);
}|code-block|syntax|javascript|1333418|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|$]]

I know this is a bit old, but I believe this method will cover all the problems and challenges stated in the comments. Credit to Eli Algranti for inspiring my work.

<pre class="lang-cs prettyprint-override"><code>/// &lt;summary&gt;Finds the type of the element of a type. Returns null if this type does not enumerate.&lt;/summary&gt;
/// &lt;param name="type"&gt;The type to check.&lt;/param&gt;
/// &lt;returns&gt;The element type, if found; otherwise, &lt;see langword="null"/&gt;.&lt;/returns&gt;
public static Type FindElementType(this Type type)
{
 if (type.IsArray)
 return type.GetElementType();

 // type is IEnumerable&lt;T&gt;;
 if (ImplIEnumT(type))
 return type.GetGenericArguments().First();

 // type implements/extends IEnumerable&lt;T&gt;;
 var enumType = type.GetInterfaces().Where(ImplIEnumT).Select(t =&gt; t.GetGenericArguments().First()).FirstOrDefault();
 if (enumType != null)
 return enumType;

 // type is IEnumerable
 if (IsIEnum(type) || type.GetInterfaces().Any(IsIEnum))
 return typeof(object);

 return null;

 bool IsIEnum(Type t) =&gt; t == typeof(System.Collections.IEnumerable);
 bool ImplIEnumT(Type t) =&gt; t.IsGenericType &amp;&amp; t.GetGenericTypeDefinition() == typeof(IEnumerable&lt;&gt;);
}
</code></pre>

blocks|key|1333458|text|public+static+Type+GetInnerGenericType(this+Type+type)
{
++//+Attempt+to+get+the+inner+generic+type
++Type+innerType+=+type.GetGenericArguments().FirstOrDefault();

++//+Recursively+call+this+function+until+no+inner+type+is+found
++return+innerType+is+null+?+type+:+innerType.GetInnerGenericType();
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1333459|这是一个递归函数，它将首先深入泛型类型列表，直到它获得一个没有内部泛型类型的具体类型定义。|unstyled|1333460|我用这个类型测试了这个方法：ICollection<IEnumerable<ICollection<ICollection<IEnumerable<IList<ICollection<IEnumerable<T>>>>>>>>|offset|length|style|CODE|1333461|它应该返回T|1333462|entityMap^0|0|0|E|2R|0|5|1|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|F|7|V|8|@$I|W|J|X|K|L]]|9|@]|A|$]]|$1|O|3|-4|5|F|7|Y|8|@]|9|@]|A|$]]]|P|$]]

<pre><code>public static Type GetInnerGenericType(this Type type)
{
 // Attempt to get the inner generic type
 Type innerType = type.GetGenericArguments().FirstOrDefault();

 // Recursively call this function until no inner type is found
 return innerType is null ? type : innerType.GetInnerGenericType();
}
</code></pre>
This is a recursive function that will go depth first down the list of generic types until it gets a concrete type definition with no inner generic types.
I tested this method with this type:
<code>ICollection&lt;IEnumerable&lt;ICollection&lt;ICollection&lt;IEnumerable&lt;IList&lt;ICollection&lt;IEnumerable&lt;T&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;</code>
which should return <code>T</code>

is there a way to retrieve type <code>T</code> from <code>IEnumerable&lt;T&gt;</code> through reflection?

e.g.

i have a variable <code>IEnumerable&lt;Child&gt;</code> info; i want to retrieve Child's type through reflection

getting type T from IEnumerable<T>

有没有办法通过反射从IEnumerable<T>中检索类型T？例如：我有一个变量Child info；我想通过反射检索IEnumerable<Child>的类型

问从IEnumerable<T>获取类型T
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