Question

正在构建一个表，其中的数据基于下拉列表的选定值。此表包含每行的复选框（默认情况下已选中）。在按钮回发上，我只想获取选中复选框的行。

在初始加载和按钮回发后，这按预期工作。但是当您在下拉列表的OnSelectedIndexChanged之后执行按钮回发时，将再次检查所有复选框。

我知道我必须让它在整个页面生命周期中运行，但是不能让它成功地工作。

我使用的代码如下： DynamicDropDownList.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="DynamicDropDownList.aspx.cs" Inherits="LittleApplication.DynamicDropDownList" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList runat="server" ID="ddlControl" OnSelectedIndexChanged="DropDownChanged" AutoPostBack="True"></asp:DropDownList><br/><br/>
        <asp:Table runat="server" ID="tblControl"></asp:Table><br/><br/>
        <asp:Button runat="server" ID="btnControl" Text="Save" 
            onclick="btnControl_Click" /><br/><br/>
        <asp:Label runat="server" ID="lblControl"></asp:Label>
    </div>
    </form>
</body>
</html>

DropDownList.aspx.cs

using System;
using System.Web.UI.WebControls;

namespace LittleApplication
{
    public partial class DynamicDropDownList : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                LoadDropDownList();
            }
            LoadTable();
        }

        private void LoadDropDownList()
        {
            ddlControl.Items.Add(new ListItem { Text = "First", Value = "1" });
            ddlControl.Items.Add(new ListItem { Text = "Second", Value = "2" });
        }

        private void LoadTable()
        {
            tblControl.Rows.Clear();

            if (ddlControl.SelectedValue == "1")
            {
                var firstCheck = new CheckBox {Checked = true};
                var firstCellCheck = new TableCell();
                firstCellCheck.Controls.Add(firstCheck);
                var firstCellText = new TableCell();
                firstCellText.Text = "First One";
                var firstRow = new TableRow();
                firstRow.Cells.Add(firstCellCheck);
                firstRow.Cells.Add(firstCellText);
                tblControl.Rows.Add(firstRow);

                var secondCheck = new CheckBox {Checked = true};
                var secondCellCheck = new TableCell();
                secondCellCheck.Controls.Add(secondCheck);
                var secondCellText = new TableCell();
                secondCellText.Text = "First Two";
                var secondRow = new TableRow();
                secondRow.Cells.Add(secondCellCheck);
                secondRow.Cells.Add(secondCellText);
                tblControl.Rows.Add(secondRow);
            }
            else
            {
                var firstCheck = new CheckBox { Checked = true };
                var firstCellCheck = new TableCell();
                firstCellCheck.Controls.Add(firstCheck);
                var firstCellText = new TableCell();
                firstCellText.Text = "Second One";
                var firstRow = new TableRow();
                firstRow.Cells.Add(firstCellCheck);
                firstRow.Cells.Add(firstCellText);
                tblControl.Rows.Add(firstRow);

                var secondCheck = new CheckBox { Checked = true };
                var secondCellCheck = new TableCell();
                secondCellCheck.Controls.Add(secondCheck);
                var secondCellText = new TableCell();
                secondCellText.Text = "Second Two";
                var secondRow = new TableRow();
                secondRow.Cells.Add(secondCellCheck);
                secondRow.Cells.Add(secondCellText);
                tblControl.Rows.Add(secondRow);   
            }
        }

        protected void DropDownChanged(object sender, EventArgs e)
        {
            lblControl.Text = String.Empty;
            LoadTable();
        }

        protected void btnControl_Click(object sender, EventArgs e)
        {
            lblControl.Text = String.Empty;
            foreach (TableRow row in tblControl.Rows)
            {
                if (((CheckBox)row.Cells[0].Controls[0]).Checked)
                {
                    lblControl.Text += row.Cells[1].Text + "<br/>";
                }
            }
        }
    }
}

要查看我描述的行为：在页面加载时，取消选中“First One”并单击“保存”。 “前两个”文本显示在“保存”按钮下（这是正确的）。将下拉列表值更改为“秒”。取消选中“Second One”，然后点击“保存”。显示了“Second One Second Two”文本，其中只有“Second Two”。

感谢您的建议。

修改我应该补充一点，这个例子模拟了实际应用程序中发生的事情的行为。它可能需要一些关于实际工作的更多反馈。下拉列表包含多个值。根据此选择，从数据库中提取不同的数据。该数据在显示的列数等方面也不同。 LoadTable将动态地将这些不同的数据添加到表中。他们唯一的共同点是使用复选框。因此，解决方案应该对LoadDropDownList和LoadTable函数进行最小的更改。

Answer 1

以下是完整代码：

using System;
using System.Web.UI.WebControls;

namespace LittleApplication
{
    public partial class DynamicDropDownList : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
if (Convert.ToString(ViewState["Generated"]) == "true")
            {
                LoadTable();
            }

            if (!IsPostBack)
            {
                LoadDropDownList();
                LoadTable();
                HideShowRow();
            }


        }

        private void LoadDropDownList()
        {
            ddlControl.Items.Add(new ListItem { Text = "First", Value = "1" });
            ddlControl.Items.Add(new ListItem { Text = "Second", Value = "2" });
        }

        private void LoadTable()
        {
            // tblControl.Rows.Clear();
            tblControl.EnableViewState = true;

            //first Options rows generation
            var firstCheck = new CheckBox { Checked = true };
            var firstCellCheck = new TableCell();
            firstCellCheck.Controls.Add(firstCheck);
            var firstCellText = new TableCell();
            firstCellText.Text = "First One";
            var firstRow = new TableRow();
            firstRow.Cells.Add(firstCellCheck);
            firstRow.Cells.Add(firstCellText);
            tblControl.Rows.Add(firstRow);

            var secondCheck = new CheckBox { Checked = true };
            var secondCellCheck = new TableCell();
            secondCellCheck.Controls.Add(secondCheck);
            var secondCellText = new TableCell();
            secondCellText.Text = "First Two";
            var secondRow = new TableRow();
            secondRow.Cells.Add(secondCellCheck);
            secondRow.Cells.Add(secondCellText);
            tblControl.Rows.Add(secondRow);

            //Second Options rows generation and intially making it hidden
            firstCheck = new CheckBox { Checked = true };
            firstCellCheck = new TableCell();
            firstCellCheck.Controls.Add(firstCheck);
            firstCellText = new TableCell();
            firstCellText.Text = "Second One";
            var thirdRow = new TableRow();
            thirdRow.Cells.Add(firstCellCheck);
            thirdRow.Cells.Add(firstCellText);
            tblControl.Rows.Add(thirdRow);

            secondCheck = new CheckBox { Checked = true };
            secondCellCheck = new TableCell();
            secondCellCheck.Controls.Add(secondCheck);
            secondCellText = new TableCell();
            secondCellText.Text = "Second Two";
            var forthRow = new TableRow();
            forthRow.Cells.Add(secondCellCheck);
            forthRow.Cells.Add(secondCellText);
            tblControl.Rows.Add(forthRow);
        }

        private void HideShowRow()
        {
            if (ddlControl.SelectedValue == "1")
            {
                //Display table row first and Second
                tblControl.Rows[0].Visible = true;
                tblControl.Rows[1].Visible = true;

                tblControl.Rows[2].Visible = false;
                tblControl.Rows[3].Visible = false;
                ((CheckBox)tblControl.Rows[2].Cells[0].Controls[0]).Checked = false;
                ((CheckBox)tblControl.Rows[3].Cells[0].Controls[0]).Checked = false;
            }
            else if (ddlControl.SelectedValue == "2")
            {
                //Display table row third and forth
                tblControl.Rows[0].Visible = false;
                tblControl.Rows[1].Visible = false;
                ((CheckBox)tblControl.Rows[0].Cells[0].Controls[0]).Checked = false;
                ((CheckBox)tblControl.Rows[1].Cells[0].Controls[0]).Checked = false;

                tblControl.Rows[2].Visible = true;
                tblControl.Rows[3].Visible = true;
            }
        }

        protected void DropDownChanged(object sender, EventArgs e)
        {
            lblControl.Text = String.Empty;
            //LoadTable();
            HideShowRow();
        }

        protected void btnControl_Click(object sender, EventArgs e)
        {
            if (Convert.ToString(ViewState["Generated"]) != "true")
            {
                LoadTable();
                ViewState["Generated"] = "true";
            }
            lblControl.Text = String.Empty;
            foreach (TableRow row in tblControl.Rows)
            {
                if (((CheckBox)row.Cells[0].Controls[0]).Checked)
                {
                    lblControl.Text += row.Cells[1].Text + "<br/>";
                }
            }
        }
     }
}

下拉列表更改选择后，动态加载的复选框值丢失

1 个答案: