c# - ASP.NET 动态生成的 TableRows 不会在回发之间持续存在

Question

在 ASPX 中

<asp:Table ID="superTable" runat="server" Width="100%">
    <%--populate me on the fly!--%>
</asp:Table>

<asp:Button ID="btnAddRow" runat="server" CausesValidation="false" Text="Add Row" onclick="btnAddRow_Click" Width="90%"/>

<asp:Button ID="btnRemoveRow" runat="server" CausesValidation="false" Text="Remove Last Row" onclick="btnRemoveRow_Click" Width="90%"/> 

<asp:Button ID="btnSubmit" runat="server" Text="1" onclick="btnSubmit_Click"  Width="90%"/>

CodeBehind 的相关位

protected void Page_Load(object sender, EventArgs e)
    {if (!IsPostBack){ writeHeader(); makeMeARow(); }}

protected void btnAddRow_Click(object sender, EventArgs e)
{   
    if (int.Parse(btnSubmit.Text) <= 20)
    {   int b = superTable.Rows.Count+1;

        writeHeader();
        btnSubmit.Text = (int.Parse(btnSubmit.Text) + 1).ToString();

        for (int a = 1; a <= int.Parse(btnSubmit.Text); a++)
            { makeMeARow(); }
    }
    else{/*tell user they can't do that! Max of 20 rows as noted by form requirements */}
}

private void writeHeader()
{
    //= == create row == =//
    TableHeaderRow tempHeaderRow = new TableHeaderRow();//make row

    //= == create cells == =//
    TableHeaderCell tempHeaderCell01 = new TableHeaderCell();
    TableHeaderCell tempHeaderCell02 = new TableHeaderCell();
    TableHeaderCell tempHeaderCell03 = new TableHeaderCell();

    tempHeaderCell01.Text = "Call Number";  tempHeaderCell01.Width = Unit.Percentage(33);
    tempHeaderCell02.Text = "Author";       tempHeaderCell02.Width = Unit.Percentage(33);
    tempHeaderCell03.Text = "Title";        tempHeaderCell03.Width = Unit.Percentage(33);

    //= == add TableCells to TableRow == =//
    tempHeaderRow.Cells.Add(tempHeaderCell01);
    tempHeaderRow.Cells.Add(tempHeaderCell02);
    tempHeaderRow.Cells.Add(tempHeaderCell03);

    //superTable.Rows.AddAt(superTable.Rows.Count, tempRow);
    superTable.Rows.Add(tempHeaderRow);
}

protected void btnRemoveRow_Click(object sender, EventArgs e)
{   int b = superTable.Rows.Count - 1;

    writeHeader();
    btnSubmit.Text = (int.Parse(btnSubmit.Text) - 1).ToString();
    for (int a = 1; a <= int.Parse(btnSubmit.Text); a++)
    {makeMeARow();}   
}
private void makeMeARow()
{
    //= == maybe off by one? == =//
    string rowCount = superTable.Rows.Count.ToString("00");

    //= == create row == =//
    TableRow tempRow = new TableRow();//make row

    //= == create cells == =//
    TableCell tempCell01 = new TableCell();
    TableCell tempCell02 = new TableCell();
    TableCell tempCell03 = new TableCell();

    //= == create TextBoxes == =//
    TextBox tempTextBox01 = new TextBox();
    TextBox tempTextBox02 = new TextBox();
    TextBox tempTextBox03 = new TextBox();

    //= == change the ID of TableRow == =//
    tempRow.ID = "tableRow_" + rowCount;

    //= == change the IDs of TableCells == =//
    tempCell01.ID = "tableCell_" + rowCount + "_01";
    tempCell02.ID = "tableCell_" + rowCount + "_02";
    tempCell03.ID = "tableCell_" + rowCount + "_03";

    //= == change the IDs of TextBoxes == =//
    tempTextBox01.ID = "txtCallNumber_" + rowCount;
    tempTextBox02.ID = "txtAuthor_" + rowCount;
    tempTextBox03.ID = "txtTitle_" + rowCount;

    //= == change TextBox widths to 90%;
    tempTextBox01.Width = Unit.Percentage(90);
    tempTextBox02.Width = Unit.Percentage(90);
    tempTextBox03.Width = Unit.Percentage(90);

    //= == add TextBoxes to TableCells == =//
    tempCell01.Controls.Add(tempTextBox01);
    tempCell02.Controls.Add(tempTextBox02);
    tempCell03.Controls.Add(tempTextBox03);

    //= == add TableCells to TableRow == =//
    tempRow.Cells.Add(tempCell01);
    tempRow.Cells.Add(tempCell02);
    tempRow.Cells.Add(tempCell03);

    //add TableRow to superTable
    //superTable.Rows.AddAt(superTable.Rows.Count, tempRow);
    superTable.Rows.Add(tempRow);
}

好的，所以，我的问题； - 当我点击“添加行”或“删除行”按钮时，单元格中的数据不会在回发之间保留。相关的行和单元格拥有相同的 ID，但不会保留数据。为什么不呢？

Answer 1

动态控件必须在每次回发时重新添加到表单中。通常这是在页面生命周期的 Init 阶段完成的。您动态添加的控件实际上具有 ViewState。当使用与之前完全相同的 ID 将适当的控件重新添加到控件树时，它应该会重新出现，并带有 ViewState 中保留的值。

查看 this article有关使用动态控件的简单提示，或者您可以从 4 Guys from Rolla 查看本教程以获得更深入的了解。