c# [key]

1. publicclass CartItem   
2.  { [Key]     
3.    public stringItemId {get; set; }         
4. publicstring CartId{ get;set; }        
5.  public intQuantity {get; set; }        
6.  public System.DateTimeDateCreated {get; set; }        
7.  public intProductId {get; set; }       
8.   public virtualProduct Product{ get;set; }      }
9. the code overrides the default behavior by using the data annotation [Key] attribute. TheKey attribute of the ItemId property specifies that the ItemID property is the primary key.
10. 解释：key 属性 标注 itemid为主属性