public string SQL = "select * from Memorandum"; protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { ViewState["SQL"] = SQL; BindData(); } if (Request.QueryString["MId"] != null) { Delete(int.Parse(Request.QueryString["MId"].ToString())); } } protected void AspNetPager1_PageChanged(object sender, EventArgs e) { BindData(); } void BindData() { PagedDataSource pds = new PagedDataSource(); IList<MemorandumInfo> Infos = new DAL.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(); } void Delete(int MId) { new Memorandum().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> protected void Button1_Click(object sender, 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 用来跟踪和保存控件的状态信息。否则这些信息可能会丢失，原因可能是这些值不随着 form 回发，或者根本就不在 page 的 html 中。
ViewState 中保存着代码中改变的控件属性，通过代码绑定到控件的任何数据，以及由用户操作触发，回发的任何更改。
ViewState 还提供了一个状态包(StateBag), 这是一个特殊的集合或字典(collection or dictionary), 可以用来保存，通过一个 key 来恢复任意的对象或者值。
赋值：ViewState[key] = value;
取值：value = ViewState[key];