创建自定义属性在C＃ [英] creating custom attribute in C#

问题描述

我已经尝试了很多次，但仍然无法理解自定义属性的使用（我已经经历了许多链接）。

I have tried lots of times but still I am not able to understand the use of custom attributes (I have already gone through lots of links).

任何人请给我解释一个有代码的自定义属性的非常基本的例子。

Can anyone please explain to me a very basic example of a custom attribute with code?

推荐答案

=http://msdn.microsoft.com/en-us/library/system.attribute.aspx>属性非常简单，了解属性是非常重要的：

While the code to create a custom Attribute is fairly simple, it's much important that you understand what are attributes:

属性是元数据编译到您的程序。属性本身不向类，属性或模块添加任何功能，只是数据。但是，使用反射，可以利用这些属性来创建功能。

Attributes are metadata compiled into your program. Attributes themselves doesn't add any functionality to a class, property or module, just data. However, using reflection, one can leverage those attributes in order to create functionality.

例如，让我们看看验证应用程序块，来自 Enterprise Library 。如果你看代码示例，你会看到：

So, for instance, let's look at Validation Application Block, from Enterprise Library. If you look at an code example, you'll see:

    /// <summary>
    /// blah blah code.
    /// </summary>
    [DataMember]
    [StringLengthValidator(8, RangeBoundaryType.Inclusive, 8, RangeBoundaryType.Inclusive, MessageTemplate = "\"{1}\" must always have \"{4}\" characters.")]
    public string Code { get; set; }

从上面的代码段中，可能会猜到代码将始终被验证，验证器的规则（在示例中，至少有8个字符，最多8个字符）。但实际上，属性不做任何事情，只是向属性添加元数据。

From the snippet above, one might guess that Code will always be validated, whenever changed, accordingly to the rules of the Validator (in the example, have at least 8 characters and at most 8 characters). But the truth is that the Attribute does nothing, only adds metadata to the property.

但是，企业库有一个 Validation.Validate 方法来查看你的对象，并且对于每个属性，它将检查内容是否违反属性通知的规则。

However, the Enterprise Library has a Validation.Validate method that will look into your object, and for each property, it'll check if the contents violates the rule informed by the attribute.

所以，这就是你应该如何考虑属性 - 一种方法来添加数据到你的代码，以后可能被其他方法/类等使用。

So, that's how you should think about attributes -- a way to add data to your code that might be later used by other methods/classes/etc.

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