c# - 在表中动态创建的文本框丢失文本值

Question

我有一个动态生成的表，在 2 列内有文本框。在回发期间，即使我填充了文本框，它们也总是空的。表是这样建的:

  protected void ddlScalaTaglie_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataTable dtRighe = oTab.getScaleTaglieRighe(ddlScalaTaglie.SelectedValue);

        //dt is datatable object which holds DB results.
        Table tbl = new Table();
        tbl.CssClass = "table table-striped  table-bordered table-responsive";

        TableRow tr;
        TableCell tcEU, tcUS, tcUK, tcQty, tcEAN;
        Label lbEU, lbUS, lbUK, lbQty, lbEAN;
        TextBox tbEU, tbUS, tbUK, tbQty, tbEAN, tbToFocus = null;

        foreach (DataRow dr in dtRighe.Rows)
        {
            tr = new TableRow();

            //ean
            tcEAN = new TableCell();
            tbEAN = new TextBox();
            tbEAN.ID = "txtEAN" + dr[0].ToString();
            tbEAN.Width = new Unit(100, UnitType.Percentage);
            tbEAN.Columns = 15;
            tcEAN.Controls.Add(tbEAN); 
            tr.Controls.Add(tcEAN);

            //Qty
            tcQty = new TableCell();
            tbQty = new TextBox(); 
            tbQty.ID = "txtQty" + dr[0].ToString(); 
            tbQty.TextMode = TextBoxMode.Number; 
            tcQty.Controls.Add(tbQty);
            tr.Controls.Add(tcQty);            

            tbl.Controls.Add(tr);
        }

        Session["tbl"] = tbl;

        divTaglieRighe.Controls.Add(tbl);
    }

当我单击“保存”按钮时，我必须遍历我的表格并保存所有 TextBox.Text...

这是我写的:

 ArrayList arrScarpaFigli = new ArrayList();
 Table tbl = (Table)Session["tbl"];
 foreach (TableRow row in tbl.Rows)
 {
     foreach (TableCell cell in row.Cells)
     {
        foreach (Control ctrl in cell.Controls)
        {
           //CONTROL IS TEXBOXT: EXTRACT VALUES//
            if (ctrl is TextBox)
            {
                TextBox txt = (TextBox)ctrl;
                arrScarpaFigli.Add(txt.Text);
             }
         }
      }
  }

问题是，如果我填充文本框，在我的文本中也总是有一个空字符串。我填充表格的唯一时刻是在下拉菜单的 selectionChange 上。

我做错了什么？提前致谢

Answer 1

您必须在每次页面加载时重新创建动态控件，以确保在 PostBack 后保留它们的值。因此，您需要创建一个新的方法来在每次加载页面时处理表的创建。

protected void Page_Load(object sender, EventArgs e)
{
    //always create the controls on every page load if there is a value selected in ddlScalaTaglie
    if (!string.IsNullOrEmpty(ddlScalaTaglie.SelectedValue))
    {
        createTable(ddlScalaTaglie.SelectedValue);
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    //use findcontrol to find the Table inside the placeholder
    Table tbl = Page.FindControl("divTaglieRighe").FindControl("Table1") as Table;

    //loop all rows and cells in the Table
    foreach (TableRow row in tbl.Rows)
    {
        foreach (TableCell cell in row.Cells)
        {
            foreach (Control ctrl in cell.Controls)
            {
                //the control is a textbox
                if (ctrl is TextBox)
                {
                    //cast the control back to a textbox
                    TextBox tb = ctrl as TextBox;

                    //does the checkbox have a value, if so append the label
                    if (!string.IsNullOrEmpty(tb.Text))
                    {
                        Label1.Text += tb.Text + "<br>";
                    }
                }
            }
        }
    }

}

protected void ddlScalaTaglie_SelectedIndexChanged(object sender, EventArgs e)
{
    //no need to create the Table dynamically, that will be handled in Page_Load
    //this method is just a dummy to trigger a PostBack

    //you could remove this method and the OnSelectedIndexChanged from the DropDown
    //and just keep the AutoPostBack="true", that will also work
}

private void createTable(string value)
{
    DataTable dtRighe = Common.LoadFromDB();

    //create a new table WITH id, that is needed for findcontrol
    Table tbl = new Table();
    tbl.ID = "Table1";

    //loop all rows in the datatable
    foreach (DataRow dr in dtRighe.Rows)
    {
        TableRow tr = new TableRow();

        //ean
        TableCell tcEAN = new TableCell();
        TextBox tbEAN = new TextBox();
        tbEAN.ID = "txtEAN" + dr[0].ToString();
        tbEAN.Width = new Unit(100, UnitType.Percentage);
        tbEAN.Columns = 15;
        tcEAN.Controls.Add(tbEAN);
        tr.Controls.Add(tcEAN);

        //Qty
        TableCell tcQty = new TableCell();
        TextBox tbQty = new TextBox();
        tbQty.ID = "txtQty" + dr[0].ToString();
        tbQty.TextMode = TextBoxMode.Number;
        tcQty.Controls.Add(tbQty);
        tr.Controls.Add(tcQty);

        tbl.Controls.Add(tr);
    }

    //add the table to the placeholder
    divTaglieRighe.Controls.Add(tbl);
}

完成示例的aspx

<asp:DropDownList ID="ddlScalaTaglie" runat="server" OnSelectedIndexChanged="ddlScalaTaglie_SelectedIndexChanged" AutoPostBack="true">
    <asp:ListItem Text="Select..." Value=""></asp:ListItem>
    <asp:ListItem Text="Option 1" Value="1"></asp:ListItem>
    <asp:ListItem Text="Option 2" Value="2"></asp:ListItem>
</asp:DropDownList>
<br />
<br />
<asp:PlaceHolder ID="divTaglieRighe" runat="server"></asp:PlaceHolder>
<br />
<br />
<asp:Button ID="Button1" runat="server" Text="Save" OnClick="Button1_Click" />
<br />
<br />
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>