如何从动态生成的文本框中检索输入值

Question

我有一个 DropDownList 与 SqlDataSource 中的项目列表绑定。在 DropDownList_SelectedIndexchanged() 函数的帮助下，我能够生成两个动态文本框。

必需输出：我需要根据用户输入的文本框搜索数据，搜索到的数据将在 Button_Click() 事件的帮助下显示在 JQGrid 中。

当前问题：未检索文本框输入，并且始终检索为空字符串“”。 获得的异常是：“AND”附近的语法不正确（SQL 查询）

如何解决这个问题？

我的aspx代码：

<asp:Panel ID="Panel5" runat="server" Height="221px">
            <span style="font-size: 135%; font-family: Verdana; font-weight: bold"> Search Functionalities </span>
            <asp:DropDownList ID="DropDownList5" runat="server" DataSourceID="column_list_for_filter" DataTextField="All_Columns" DataValueField="All_Columns" OnSelectedIndexChanged ="DropDownList5_SelectedIndexChanged"  AutoPostBack="true">
            </asp:DropDownList>
            <asp:SqlDataSource ID="column_list_for_filter" runat="server" ConnectionString="<%$ ConnectionStrings:DatabaseConnectionString %>" SelectCommand="SELECT COLUMN_NAME 'All_Columns' FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME='RESULT'  "></asp:SqlDataSource>
            <asp:Button ID="Button1" runat="server" Font-Bold="True" Font-Names="Arial" Font-Size="Small" OnClick="Button1_Click" Text="Search Flow Periods" Width="144px" />
            <asp:Table ID="dynamic_filter_table" runat="server" ToolTip="Results">
            </asp:Table>
</asp:Panel>

我的 C# 代码：

//Creation of Two Dynamic Text Box Web Controls on DDL selection
     protected void DropDownList5_SelectedIndexChanged(object sender, EventArgs e)
     {
         createdynamiccontrols();

     }

    /*Two Text Boxes and Two Labels for input and search the FlowPeriod and display in JqGrid      
    thru button click event*/
     protected void createdynamiccontrols()//(string ID1, string ID2)
     {
         int i = DropDownList5.SelectedIndex;
         ++i;
         TableRow row;
         row = new TableRow();
         TableCell cell1 ;
         cell1 = new TableCell();
         TableCell cell2;
         cell2= new TableCell();
         // Set a unique ID for each TextBox added
         TextBox tb1;
         tb1 = new TextBox();
         TextBox tb2;
         tb2 = new TextBox();
         Label lbl1;
         lbl1 = new Label();
         Label lbl2;
         lbl2 = new Label();
         // Set a unique ID for each TextBox added      
         tb1.ID = "lowerbound_" + i.ToString();
         tb2.ID = "upperbound_"+ i.ToString() ;
         lbl1.Text = "LowerBound:";
         lbl1.Font.Size = FontUnit.Point(10);
         lbl1.Font.Bold = true;
         lbl1.Font.Name = "Arial";
         lbl2.Text = "UpperBound:";
         lbl2.Font.Size = FontUnit.Point(10);
         lbl2.Font.Bold = true;
         lbl2.Font.Name = "Arial";
         // Add the control to the TableCell       
         cell1.Controls.Add(lbl1);
         cell1.Controls.Add(tb1);
         cell2.Controls.Add(lbl2);
         cell2.Controls.Add(tb2);
         // Add the TableCell to the TableRow  
         row.Cells.Add(cell1);
         row.Cells.Add(cell2);
         dynamic_filter_table.Rows.Add(row);
         dynamic_filter_table.EnableViewState = true;
         ViewState["dynamic_filter_table"] = true;
         Button1.EnableViewState = true;
         ViewState["Button_1"] = true;
     }

     protected override object SaveViewState()
     {
         object[] viewstate = new object[2];
         List<string> dynamic_text_values  = new List<string>();
         foreach (TableRow row in dynamic_filter_table.Controls)
         {
             foreach (TableCell cell in row.Controls)
             {
                 if (cell.Controls[1] is TextBox)
                 {
                     dynamic_text_values.Add(((TextBox)cell.Controls[1]).Text);
                 }
             }
         }
         viewstate[0] = dynamic_text_values.ToArray();
         viewstate[1] = base.SaveViewState();
         return viewstate;
     }

    protected override void LoadViewState(object savedState)
     {
         if (savedState is object[] && ((object[])savedState).Length == 2 && ((object[])savedState)[0] is string[])
         {
             object[] newViewState = (object[])savedState;
             string[] txtValues = (string[])(newViewState[0]);
             if (txtValues.Length > 0)
             {
                createdynamiccontrols();

             }
             base.LoadViewState(newViewState[1]);
         }
         else
         {
             base.LoadViewState(savedState);
         }
     }


     protected void Button1_Click(object sender, EventArgs e)
    {
        createdynamiccontrols();                 
        int j = DropDownList5.SelectedIndex;
        ++j;
        Panel6.Visible = true;
        JQGrid9.Visible = true;
        TextBox lowerboundd = dynamic_filter_table.FindControl("lowerbound_" + j.ToString()) as TextBox;
        TextBox upperbound = dynamic_filter_table.FindControl("upperbound_" + j.ToString()) as TextBox;
        string testt = lowerboundd.Text;
        con.Open();
        SqlDataAdapter da = new SqlDataAdapter("SELECT ColumnName1,Columnname2 FROM RESULT WHERE " + DropDownList5.SelectedValue + " >= " + lowerboundd.Text + " AND " + DropDownList5.SelectedValue + " <= " + upperbound.Text, con);
        DataSet ds = new DataSet();
        da.Fill(ds);

        /*Error occurs here as Incorrect Syntax near AND as the string obtained is "" and not          
        textbox inputs*/

        con.Close();
        Session["DataforSearch"] = ds.Tables[0];

     }

protected void Page_Load(object sender, EventArgs e)
    {           
        //Dynamic controls creation on Page Load
        if (!IsPostBack)
        {
            BindDropDownLists();

        } 
        dynamic_filter_table.EnableViewState = true;
    }

Answer 1

您需要将BindDropDownLists(); 从 Page_Load 移至 Page_Init 方法，否则页面生命周期将找不到视图状态并附加到您的控件。当您进入 Page_Load 时，您已经太迟了。确保在 init 中创建控件的逻辑以及在加载/事件中检索数据的逻辑，您应该会看到一些结果。

您不需要 viewstate 的东西，因为它会自动连接起来，您不能在 click 或 selectedindexchanged 等控件事件中创建动态控件，因为在生命周期中为时已晚。动态控件需要在加载之前创建，以便在加载到来时连接视图状态。

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