Viewstate 的用法

 1.做了开发这么久，居然不知道Viewstate是怎么用的！真悲剧……

Viewstate主要是用来保留页面数据的。下面是某一种情况的用法。

        private string MCategory
        {
            set
            {
                ViewState["MCategory"] = value;
            }
            get
            {
                if (ViewState["MCategory"] == null)
                    return "";
                else
                    return (string)ViewState["MCategory"];
            }
        }
        //save market category information
        private string KCategory
        {
            set
            {
                ViewState["KCategory"] = value;
            }
            get
            {
                if (ViewState["KCategory"] == null)
                    return "";
                else
                    return (string)ViewState["KCategory"];
            }
        }

 附带一个添加多行的方式，以前见过，没有记下来，都忘记了，悲剧……

    private string GetCondition
    {
        get
        {
            return @"<Where>  
          <And>  
            <And>  
             <Geq>  
                   <FieldRef Name='Created' />  
                    <Value Type='DateTime'>{0}</Value>  
             </Geq>  
             <Leq>  
                 <FieldRef Name='Created' />  
                <Value Type='DateTime'>{1}</Value>  
             </Leq>  
             </And>  
              <Gt>  
               <FieldRef Name='ID' />  
               <Value Type='Counter'>0</Value>  
              </Gt>  
          </And>  
            </Where>";
        }
    }