ASP.NET动态生成的TableRows在回发之间不会保留 [英] ASP.NET dynamically-generated TableRows won't persist between postbacks

问题描述

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

Relevant bits of CodeBehind

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，单元格中的数据在回发之间不会持续存在.相关的行和单元格具有相同的ID，但不保留数据.为什么不呢?

Okay, so, my problem; -when I hit either the "Add Row" or "Remove Row" button, the data in the cells don't persist between postbacks. The relevant rows and cells hold the same IDs, but don't persist data. Why not?

推荐答案

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.您动态添加的控件确实具有ViewState.当使用与以前完全相同的ID将适当的控件重新添加到控件树时，它应该重新出现，并带有ViewState中保留的值.

Dynamic controls must be re-added to the form on each postback. Typically this is done during the Init phase of the page's lifecycle. The controls that you have added dynamically DO actually have ViewState. When the appropriate control is re-added to the control tree using the exact same ID it had before, it should reappear with the values that were persisted in ViewState.

查看本文，以获取有关使用动态广告的简单提示控件，或者您可以从 4名来自Rolla的人中查看本教程，以了解更多信息深入了解.

Check out this article for simple tips on using dynamic controls or you can check out this tutorial from 4 Guys from Rolla for a more in-depth look.

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