[AttributeUsage(AttributeTargets.All)]//指定Attribute的使用范围，比如只能在class级别使用public class Column : Attribute{    public Column(string str)    {        this.str = str;    }    public string str { get; set; }}//第2个[AttributeUsage(AttributeTargets.All)]public class Table : Attribute{    public Table(string str)    {        this.str = str;    }    public string str { get; set; }}//2个属性[Column("class")][Table("table class")]public class Abc{    public string x { get; set; }    [Column("attr")]    public Int32 y { get; set; }}protected void Page_Load(object sender, EventArgs e){    //通过反射可以调用到这个类型头上的attr    Type type = typeof(Abc);
    bool isGot = Attribute.IsDefined(type, typeof(Column)); //查看有没有某个Attribute    Attribute[] attrs = Attribute.GetCustomAttributes(type); //批量获取    string xy =  attrs.First().GetType().Name; //可以查看它的名字来选择想要的，或是看有没有想要的.    Column column = (Column)Attribute.GetCustomAttribute(type, typeof(Column)); //强转    Column[] columns = (Column[])Attribute.GetCustomAttributes(type, typeof(Column));    column = columns[0];    string x = column.str; //调用方法或是公开属性等等都可以            //实例化之后也是可以一样拿    Abc a = new Abc();    PropertyInfo info = a.GetType().GetProperty("y");     Column attribute2 = (Column)Attribute.GetCustomAttribute(info, typeof(Column));    string xyz = attribute2.str;}