Csharp/C Sharp by API/System/Attribute

Attribute.GetCustomAttribute

 
using System;  
using System.Reflection; 
  
[AttributeUsage(AttributeTargets.All)] 
class RemarkAttribute : Attribute { 
  string remarkValue; // underlies remark property 
 
  public string supplement; // this is a named parameter 
 
  public RemarkAttribute(string comment) { 
    remarkValue = comment; 
    supplement = "None"; 
  } 
 
  public string remark { 
    get { 
      return remarkValue; 
    } 
  } 
}  
 
[RemarkAttribute("This class uses an attribute.", 
                 supplement = "This is additional info.")] 
class UseAttrib { 
  // ... 
} 
 
public class NamedParamDemo {  
  public static void Main() {  
    Type t = typeof(UseAttrib); 
 
    Console.Write("Attributes in " + t.Name + ": "); 
 
    object[] attribs = t.GetCustomAttributes(false);  
    foreach(object o in attribs) { 
      Console.WriteLine(o); 
    } 
 
    // Retrieve the RemarkAttribute. 
    Type tRemAtt = typeof(RemarkAttribute); 
    RemarkAttribute ra = (RemarkAttribute) 
          Attribute.GetCustomAttribute(t, tRemAtt); 
 
    Console.Write("Remark: "); 
    Console.WriteLine(ra.remark); 
 
    Console.Write("Supplement: "); 
    Console.WriteLine(ra.supplement); 
  }  
}

Attribute.GetCustomAttribute(Type t, Type tR);

 
using System;  
using System.Reflection; 
  
[AttributeUsage(AttributeTargets.All)] 
public class MyAttribute : Attribute { 
  public string remark;
 
  public string supplement; 
 
  public MyAttribute(string comment) { 
    remark = comment; 
    supplement = "None"; 
  } 
 
  public string Remark { 
    get { 
      return remark; 
    } 
  } 
}  
 
[MyAttribute("This class uses an attribute.", 
                 supplement = "This is additional info.")] 
class UseAttrib { 
} 
 
class MainClass {  
  public static void Main() {  
    Type t = typeof(UseAttrib); 
 
    Console.Write("Attributes in " + t.Name + ": "); 
 
    object[] attribs = t.GetCustomAttributes(false);  
    foreach(object o in attribs) { 
      Console.WriteLine(o); 
    } 
 
    // Retrieve the MyAttribute. 
    Type tRemAtt = typeof(MyAttribute); 
    MyAttribute ra = (MyAttribute) 
          Attribute.GetCustomAttribute(t, tRemAtt); 
 
    Console.Write("Remark: "); 
    Console.WriteLine(ra.remark); 
 
    Console.Write("Supplement: "); 
    Console.WriteLine(ra.supplement); 
  }  
}

Attribute.Remove()

 
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Linq;
public class MainClass {
    public static void Main() {
        XElement firstParticipant;
        XDocument xDocument = new XDocument(
          new XElement("Books", firstParticipant =
            new XElement("Book",
              new XAttribute("type", "Author"),
              new XElement("FirstName", "J"),
              new XElement("LastName", "R"))));
        Console.WriteLine(xDocument);
        firstParticipant.Attribute("type").Remove();
        Console.WriteLine(xDocument);
    }
}

Attribute.Value

 
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Linq;
public class MainClass {
    public static void Main() {
        XElement firstParticipant;
        XDocument xDocument  = new XDocument(
          new XElement("Books", firstParticipant =
            new XElement("Book",
              new XAttribute("type", "Author"),
              new XAttribute("experience", "first-time"),
              new XElement("FirstName", "J"),
              new XElement("LastName", "R"))));
        Console.WriteLine(xDocument);
        firstParticipant.Attribute("experience").Value = "beginner";
        Console.WriteLine(xDocument);
    }
}

extends Attribute

 
using System;

public class MainClass 
{
    public static void Main() 
    {
        UnitTest u;
        Console.Write("Class1 UnitTest attribute: ");
        u = (UnitTest) Attribute.GetCustomAttribute(typeof(Class1), typeof(UnitTest));
        Console.WriteLine(u.Written());
        Console.Write("Class2 UnitTest attribute: ");
        u = (UnitTest) Attribute.GetCustomAttribute(typeof(Class2), typeof(UnitTest));
        Console.WriteLine(u.Written());
    }
}

public class UnitTest : Attribute
{
    bool bWritten;
    public bool Written()
    {
        return bWritten;
    }
    public UnitTest(bool Written)
    {
        bWritten = Written;
    }
}
// apply the UnitTest attribute to two classes
[UnitTest(true)]
public class Class1
{
}
[UnitTest(false)]
public class Class2
{
}