Button Click in a TableCell never fires and table disappears

问题

I my ASP.NET Webforms app, I have a table in which I add all data dynamically. One row contains Buttons in each cell. I want the button to fire onclick event when the user clicks on it. But, with the below code, the event never fires and the table disappears. Here's the code :

    <asp:Table ID="floorTable" runat="server"  Width="100%" GridLines="Both">
    </asp:Table>

In Code behind

   // This method is called on a DropDownList SelectedItemChanged Event - so
   // the buttons cannot be created in Page_Load or so. Have to create 
   // totally based on the DropDown selected item.
    private void PopulateFloorRow(int floorNo, FloorPattern fp)
    {
        int cols = fp.UnitPattern.Count;

        // HEADER ROW
        TableRow thead = new TableRow(); 
        thead.Width = Unit.Percentage(100);
        thead.TableSection = TableRowSection.TableHeader;
        TableCell theadCell = new TableCell();
        theadCell.ColumnSpan = cols;
        Label title = new Label();
        title.Text = "Floor # " + floorNo;
        theadCell.Controls.Add(title);
        thead.Controls.Add(theadCell);

        TableRow planRow = GetFloorPlan(floorNo, fp);

        TableRow tr = new TableRow();
        TableCell tc = null;
        int tcWidPerc = (int)fp.UnitPattern.Count / 100;

        foreach (UnitPattern up in fp.UnitPattern)
        {                
            tc = new TableCell();

            Button imgBtn = new Button();

            // On Adding BELOW Line - ERROR - 0x800a1391 - JavaScript runtime error: 'UnitLinkClicked' is undefined
            //imgBtn.Attributes.Add("onClick", "UnitLinkClicked(this)");

            imgBtn.CommandArgument = up.UnitPatternId.ToString(); // I want to know which button is pressed. So, sort of Tag
            imgBtn.Click += new EventHandler(UnitLinkClicked);
            imgBtn.BorderWidth = Unit.Pixel(10);
            imgBtn.BorderColor = Color.Transparent;
            imgBtn.Width = Unit.Percentage(100);
            if (up.UnitNo != null)
            {
                imgBtn.Text = up.UnitNo;
            }

            tc.Controls.Add(imgBtn);

            tr.Controls.Add(tc);
        }

        floorTable.Rows.Add(thead);
        floorTable.Rows.Add(planRow);
        floorTable.Rows.Add(tr);

        // Create Footer
        PopulateTableFooter(cols);

    }

    protected void UnitLinkClicked(object sender, EventArgs e)
    {
        Button btn = (Button)(sender);
        string upId = btn.CommandArgument;

        System.Diagnostics.Debug.WriteLine("LINK Button clicked Of UP ID :" + upId);
    }

EDIT : CODE OF SELECTEDiNDEXCHANGED ADDED

My DropDown_SelectedIndexChanged Code :

    protected void floorDropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (selectedProject == null)
            selectedProject = _db.Projects.Find(projectsList.SelectedValue);

        System.Diagnostics.Debug.WriteLine("SELCTED Project = " + selectedProject.ProjectId);

        // "Select Floor" is selected, so Hide floor Table
        if (floorDropDownList.SelectedValue == "-1")
        {
            floorTable.Visible = false;
        }
        else
        {
            int floorNo = int.Parse(floorDropDownList.SelectedValue);
            if (floorNo > 0)
            {
                PopulateFloorRow(floorNo, (FloorPattern)selectedProject.FloorPattern.ElementAt(floorNo - 1));
            }
        }
    }

If I had selected "3" in my drop down, the table appears as expected. I click on a button and the table disappears, but the value in the drop down in still "3" only.

EDIT PART OVER

With the above code, I when I click on a button, the UnitLinkClicked event is never fired (I had added breakpoint) and the whole table disappears.

Can you say what problem can this be ? A button by default is meant to be AutoPostBack & it doesn't have that property too. What am I missing here and how to solve this. Am stuck on this since days and trying to figure out.

Any help is highly appreciated. Thanks

回答1:

You need to set an ID for your button. Without the ID the event will not be fired.

Button imgBtn = new Button();
imgBtn.ID = "imgBtn";

Also make sure that each button you add has a unique ID. You could probably concatenate the floor no. or any other fields to arrive at a unique name.

Also, the table will disappear unless, you manage that in your Page_Load. You need to reload the table if the DropDown has a selected index.

EDIT: Code Sample

.cs code

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack)
    {
        PopulateFloorRow();
    }
}        

protected void cmb_SelectedIndexChanged(object sender, EventArgs e)
{
    PopulateFloorRow();
}

private void PopulateFloorRow()
{
    floorTable.Rows.Clear();

    for (int i = 0; i < 2; i++)
    {
        TableRow tableRow = new TableRow();
        tableRow.Cells.Add(new TableCell());
        tableRow.Cells.Add(new TableCell());

        tableRow.Cells[0].Controls.Add(new Label() { Text = cmb.SelectedItem.Text });
        Button button = new Button();
        button.ID = "btn" + i.ToString();
        button.Text = "Click";
        button.Click += button_Click;
        tableRow.Cells[1].Controls.Add(button);
        floorTable.Rows.Add(tableRow);
    }

}

void button_Click(object sender, EventArgs e)
{
    throw new NotImplementedException();
}

.aspx code

<asp:DropDownList id="cmb" runat="server" OnSelectedIndexChanged="cmb_SelectedIndexChanged" AutoPostBack="true"><asp:ListItem>One</asp:ListItem><asp:ListItem>Two</asp:ListItem></asp:DropDownList>
<asp:Table ID="floorTable" runat="server"  Width="100%" GridLines="Both">
</asp:Table>

来源：https://stackoverflow.com/questions/29350069/button-click-in-a-tablecell-never-fires-and-table-disappears

标签

ASP.NET

button

dynamic

onclick