| 发表于：2007-08-03 00:55:169楼 得分:0 |
what are attributes?
attributes describe a type, method, or property in a way that can be programmatically queried using a technique called reflection. some common uses for attributes are to
specify which security privileges a class requires
specify security privileges to refuse to reduce security risk
declare capabilities, such as supporting serialization
describe the assembly by providing a title, description, and copyright notice
attribute types derive from the system.attribute base class and are specified using <> or [] notation. the following code sample demonstrates how to add assembly attributes:
' vb assemblyinfo.vb
<assembly: assemblytitle（ "ch01vb ")>
<assembly: assemblydescription（ "chapter 1 samples ")>
<assembly: assemblycompany（ "microsoft learning ")>
<assembly: assemblyproduct（ "ch01vb ")>
<assembly: assemblycopyright（ "copyright © 2006 ")>
<assembly: assemblytrademark（ " ")>
// c# - assemblyinfo.cs
[assembly: assemblytitle（ "ch01cs ")]
[assembly: assemblydescription（ "chapter 1 samples ")]
[assembly: assemblyconfiguration（ " ")]
[assembly: assemblycompany（ "microsoft learning ")]
[assembly: assemblyproduct（ "ch01cs ")]
[assembly: assemblycopyright（ "copyright © 2006 ")]
[assembly: assemblytrademark（ " ")]
visual studio automatically creates some standard attributes for your assembly when you create a project, including a title, description, company, guide, and version. you should edit these attributes for every project you create because the defaults do not include important information such as the description.
attributes do more than describe an assembly to other developers, they can also declare requirements or capabilities. for example, to enable a class to be serialized, you must add the serializable attribute, as the following code demonstrates:
' vb
<serializable（)> class shoppingcartitem
end class
// c#
[serializable]
class shoppingcartitem
{
}
without the serializable attribute, a class is not serializable. similarly, the following code uses attributes to declare that it needs to read the c:\boot.ini file. because of this attribute, the runtime will throw an exception prior to ＥＸＥＣution if it lacks the specified privilege:
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