this 关键字引用类的当前实例，还可用作扩展方法的第一个参数的修饰符。

对实例的引用略过，下面给出扩展方法的例子：

 

1  public static ObservableCollection
     
       ArrayToObservableCollection
      
       ( this T[] list) 2         { 3             if (list == null) 4                 return null; 5             ObservableCollection
       
         collections = new ObservableCollection
        
         (); 6             foreach (var item in list) 7             { 8                 collections.Add(item); 9             }10             return collections;11         }12 13         public static ObservableCollection
         
           ListToObservableCollection
          
           (this List
           
             list)14 {15 if (list == null)16 return null;17 ObservableCollection
            
              collections = new ObservableCollection
             
              ();18 foreach (var item in list)19 {20 collections.Add(item);21 }22 return collections;23 }24 25 public static List
              
                ObservableCollectionToList
               
                (this ObservableCollection
                
                  col)26 {27 if (col == null)28 return null;29 List
                 
                   lst = new List
                  
                   ();30 foreach (var item in col)31 {32 lst.Add(item);33 }34 return lst;35 }