blocks|key|62846|text|有两种可能性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|62847|您真的没有Label属性。|offset|length|style|CODE|62848|您需要调用适当的GetProperty+overload并传递正确的绑定标志，例如BindingFlags.Public+%7C+BindingFlags.Instance|62849|如果您的属性不是公共属性，则需要使用BindingFlags.NonPublic或其他适合您的用例的标志组合。请阅读参考的API文档以了解详细信息。|62850|编辑：|62851|哦，刚刚注意到你在typeof(MyClass)上调用了GetProperty。typeof(MyClass)是Type，它肯定没有Label属性。|62852|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/zy0d4103.aspx^0|0|5|5|0|15|17|8|K|0|0|I|M|0|0|9|F|S|B|14|F|1K|4|1U|5|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@$D|Z|E|10|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@$D|14|E|15|1|16]]|A|$]]|$1|J|3|K|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1A|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1B|8|@$D|1C|E|1D|F|G]|$D|1E|E|1F|F|G]|$D|1G|E|1H|F|G]|$D|1I|E|1J|F|G]|$D|1K|E|1L|F|G]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]]]

There are 2 possibilities.

You really don't have <code>Label</code> property.

You need to call appropriate <a href="http://msdn.microsoft.com/en-us/library/zy0d4103.aspx" rel="nofollow">GetProperty overload</a> and pass the correct binding flags, e.g. <code>BindingFlags.Public | BindingFlags.Instance</code>

If your property is not public, you will need to use <code>BindingFlags.NonPublic</code> or some other combination of flags which fits your use case. Read the referenced API docs to find the details.

EDIT:

ooops, just noticed you call <code>GetProperty</code> on <code>typeof(MyClass)</code>. <code>typeof(MyClass)</code> is <code>Type</code> which for sure has no <code>Label</code> property.

blocks|key|854530|text|您的方法如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|854531|public+static+bool+HasProperty(this+object+obj,+string+propertyName)
{
++++return+obj.GetType().GetProperty(propertyName)+!=+null;
}|code-block|syntax|javascript|854532|这为object添加了一个扩展--所有东西的基类。当您调用此扩展时，您正在向它传递一个Type|offset|length|style|CODE|854533|var+res+=+typeof(MyClass).HasProperty("Label");|854534|您的方法需要一个类的实例，而不是Type。否则你基本上就是在做|854535|typeof(MyClass)+-+this+gives+an+instanceof+`System.Type`.+|854536|然后|854537|type.GetType()+-+this+gives+`System.Type`
Getproperty('xxx')+-+whatever+you+provide+as+xxx+is+unlikely+to+be+on+`System.Type`|854538|正如@PeterRitchie正确指出的那样，在这一点上，您的代码正在System.Type上查找属性Label。该属性不存在。|854539|解决方案是|854540|a)为扩展提供一个MyClass实例：|854541|var+myInstance+=+new+MyClass()
myInstance.HasProperty("Label")|854542|b)将扩展放在System.Type上|854543|public+static+bool+HasProperty(this+Type+obj,+string+propertyName)
{
++++return+obj.GetProperty(propertyName)+!=+null;
}|854544|和|854545|typeof(MyClass).HasProperty("Label");|854546|entityMap^0|0|0|2|6|17|4|0|0|G|4|0|0|0|0|Z|B|1F|5|0|0|0|0|7|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1F|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1G|8|@$I|1H|J|1I|K|L]|$I|1J|J|1K|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1M|8|@$I|1N|J|1O|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1P|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1R|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1S|8|@$I|1T|J|1U|K|L]|$I|1V|J|1W|K|L]]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1X|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|12|3|13|5|D|7|1Z|8|@]|9|@]|A|$E|F]]|$1|14|3|15|5|6|7|20|8|@$I|21|J|22|K|L]]|9|@]|A|$]]|$1|16|3|17|5|D|7|23|8|@]|9|@]|A|$E|F]]|$1|18|3|19|5|6|7|24|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|D|7|25|8|@]|9|@]|A|$E|F]]|$1|1C|3|-4|5|6|7|26|8|@]|9|@]|A|$]]]|1D|$]]

Your method looks like this:

<pre><code>public static bool HasProperty(this object obj, string propertyName)
{
 return obj.GetType().GetProperty(propertyName) != null;
}
</code></pre>

This adds an extension onto <code>object</code> - the base class of everything. When you call this extension you're passing it a <code>Type</code>:

<pre><code>var res = typeof(MyClass).HasProperty("Label");
</code></pre>

Your method expects an instance of a class, not a <code>Type</code>. Otherwise you're essentially doing

<pre><code>typeof(MyClass) - this gives an instanceof `System.Type`. 
</code></pre>

Then

<pre><code>type.GetType() - this gives `System.Type`
Getproperty('xxx') - whatever you provide as xxx is unlikely to be on `System.Type`
</code></pre>

As @PeterRitchie correctly points out, at this point your code is looking for property <code>Label</code> on <code>System.Type</code>. That property does not exist.

The solution is either

a) Provide an instance of MyClass to the extension:

<pre><code>var myInstance = new MyClass()
myInstance.HasProperty("Label")
</code></pre>

b) Put the extension on <code>System.Type</code>

<pre><code>public static bool HasProperty(this Type obj, string propertyName)
{
 return obj.GetProperty(propertyName) != null;
}
</code></pre>

and

<pre><code>typeof(MyClass).HasProperty("Label");
</code></pre>

blocks|key|5537704|text|这回答了一个不同的问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5537705|如果试图找出一个对象(而不是类)是否具有属性，|5537706|OBJECT.GetType().GetProperty("PROPERTY")+!=+null|code-block|syntax|javascript|5537707|如果(但不仅仅是如果)属性存在，则返回true。|5537708|在我的例子中，我在一个ASP.NET+MVC局部视图中，并且希望在属性不存在或者属性(布尔值)为真的情况下呈现一些东西。|5537709|@if+((Model.GetType().GetProperty("AddTimeoffBlackouts")+==+null)+%7C%7C
++++++++Model.AddTimeoffBlackouts)|5537710|帮了我大忙。|5537711|编辑:现在，使用nameof操作符而不是字符串化的属性名可能更明智。|offset|length|style|CODE|5537712|entityMap^0|0|0|0|0|0|0|0|8|6|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|13|8|@]|9|@]|A|$G|H]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|15|8|@$S|16|T|17|U|V]]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

This answers a different question:

If trying to figure out if an OBJECT (not class) has a property, 

<pre><code>OBJECT.GetType().GetProperty("PROPERTY") != null
</code></pre>

returns true if (but not only if) the property exists.

In my case, I was in an ASP.NET MVC Partial View and wanted to render something if either the property did not exist, or the property (boolean) was true.

<pre><code>@if ((Model.GetType().GetProperty("AddTimeoffBlackouts") == null) ||
 Model.AddTimeoffBlackouts)
</code></pre>

helped me here.

Edit: Nowadays, it's probably smart to use the <code>nameof</code> operator instead of the stringified property name.

blocks|key|5537729|text|如果你像我一样绑定：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5537730|<%25#+Container.DataItem.GetType().GetProperty("Property1")+!=+null+?+DataBinder.Eval(Container.DataItem,+"Property1")+:+DataBinder.Eval(Container.DataItem,+"Property2")++%25>|code-block|syntax|javascript|5537731|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|$]]

If you are binding like I was:

<pre><code>&lt;%# Container.DataItem.GetType().GetProperty("Property1") != null ? DataBinder.Eval(Container.DataItem, "Property1") : DataBinder.Eval(Container.DataItem, "Property2") %&gt;
</code></pre>

blocks|key|854595|text|在绑定被接受的答案时，我得到了这样的错误：“类型不包含GetProperty的定义”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|854596|这就是我最终得到的结论：|854597|using+System.Reflection;

if+(productModel.GetType().GetTypeInfo().GetDeclaredProperty(propertyName)+!=+null)
{

}|code-block|syntax|javascript|854598|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I got this error: "Type does not contain a definition for GetProperty" when tying the accepted answer.

This is what i ended up with:

<pre><code>using System.Reflection;

if (productModel.GetType().GetTypeInfo().GetDeclaredProperty(propertyName) != null)
{

}
</code></pre>

blocks|key|2186587|text|我不确定为什么需要这样做的上下文，所以这可能不会为您返回足够的信息，但这是我能够做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2186588|if(typeof(ModelName).GetProperty("Name+of+Property")+!=+null)
{
//whatevver+you+were+wanting+to+do.
}|code-block|syntax|javascript|2186589|在我的例子中，我正在运行表单提交的属性，如果条目为空，也有默认值可以使用-所以我需要知道是否有要使用的值-我在模型中给所有默认值加上了default前缀，所以我需要做的就是检查是否有以该值开头的属性。|2186590|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I'm unsure of the context on why this was needed, so this may not return enough information for you but this is what I was able to do:

<pre><code>if(typeof(ModelName).GetProperty("Name of Property") != null)
{
//whatevver you were wanting to do.
}
</code></pre>

In my case I'm running through properties from a form submission and also have default values to use if the entry is left blank - so I needed to know if the there was a value to use - I prefixed all my default values in the model with Default so all I needed to do is check if there was a property that started with that.

I try to know if a property exist in a class, I tried this :

<pre><code>public static bool HasProperty(this object obj, string propertyName)
{
 return obj.GetType().GetProperty(propertyName) != null;
}
</code></pre>

I don't understand why the first test method does not pass ?

<pre><code>[TestMethod]
public void Test_HasProperty_True()
{
 var res = typeof(MyClass).HasProperty("Label");
 Assert.IsTrue(res);
}

[TestMethod]
public void Test_HasProperty_False()
{
 var res = typeof(MyClass).HasProperty("Lab");
 Assert.IsFalse(res);
}
</code></pre>

Check if a property exists in a class

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我尝试知道一个属性是否存在于类中，我尝试这样做：public static bool HasProperty(this object obj, string propertyName){    return obj.GetType().GetProperty(propertyName) != null;}我不明白为什么...

问检查类中是否存在属性
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问检查类中是否存在属性EN