Aspnetpager Query paging problem (click Page number, no longer the data set after query) viewstate resolve

publicstringSQL = "select * from Memorandum";      protectedvoidPage_Load(objectsender, EventArgs e)      {          if(!IsPostBack)          {              ViewState["SQL"] = SQL;              BindData();          }          if(Request.QueryString["MId"] != null)          {              Delete(int.Parse(Request.QueryString["MId"].ToString()));          }      }      protectedvoidAspNetPager1_PageChanged(object sender, EventArgs e)      {          BindData();      }           voidBindData()      {          PagedDataSource pds = newPagedDataSource();          IList<MemorandumInfo> Infos = newDAL.Memorandum().GetAllMemorandumsBySQL(ViewState["SQL"].ToString());          pds.DataSource = Infos;          pds.AllowPaging = true;          pds.PageSize = 10;//取控件的分页大小          pds.CurrentPageIndex = this.AspNetPager1.CurrentPageIndex - 1;//显示当前页          //设置控件          this.AspNetPager1.RecordCount = Infos.Count;//记录总数          this.AspNetPager1.PageSize = 10;          Repeater1.DataSource = pds;          Repeater1.DataBind();      }      voidDelete(intMId)      {          newMemorandum().DeleteMemorandum(MId);          Response.Write("<script>alert(‘成功删除该条备忘信息‘);location=‘?‘;</script>");      }      /// <summary>      /// 查询      /// </summary>      /// <param name="sender"></param>      /// <param name="e"></param>      protectedvoidButton1_Click(objectsender, EventArgs e)      {          if (DropDownList1.SelectedValue == "0")          {              ViewState["SQL"] = "select * from Memorandum";              BindData();          }          else          {              ViewState["SQL"] = "SELECT   MId, MemoTitle, MemoContent, MemoStartTime, MemoEndTime FROM  Memorandum WHERE (MemoEndTime - NOW() <=7)";              BindData();          }      }  }

ViewState is used to track and save state information for a control. Otherwise, this information may be lost, either because the values are not being sent back with the form or are not in the HTML of the page at all.
ViewState holds the changed control properties in the code, any data that is bound to the control by code, and any changes that are triggered by the user action and postback.
ViewState also provides a status pack (StateBag), which is a special set or dictionary (collection or dictionary) that can be used to save and restore arbitrary objects or values through a key.

Assignment: Viewstate[key] = value;

Value: value = Viewstate[key];

(GO) Aspnetpager Query paging problem (click Page number, no longer the data set after query) viewstate resolve