Dynamically Created Button refuses to call it's onClick

Question

So while fooling around with webforms, I tried to create a page that outputs a table from a sql server to a html table on Page_Load. I then tried to add a button to a column which would redirect to a page. The only problem is, when I press the button nothing happens at all... I've tried putting breakpoints at the onclick method but they are never reached.

        num = ds.Tables[0].Rows.Count;
        htmlTable.Append("<tr style='background-color:#bd0000; color: White;'><th>ID</th><th>Job #</th><th>Project</th><th>Completed By</th><th>Date Created</th><th></th></tr>");

        if (!object.Equals(ds.Tables[0], null))
        {
            if (ds.Tables[0].Rows.Count > 0)              
            {
                int MAX_VIEW = (ds.Tables[0].Rows.Count > 15) ? 15 : ds.Tables[0].Rows.Count;
                for (int i = 0; i < MAX_VIEW; i++)
                {
                    htmlTable.Append("<td>" + ds.Tables[0].Rows[i]["CCPOF_ID"] + "</td>");
                    htmlTable.Append("<td>" + ds.Tables[0].Rows[i]["Job_Number"] + "</td>");
                    htmlTable.Append("<td>" + ds.Tables[0].Rows[i]["Project_Name"] + "</td>");
                    htmlTable.Append("<td>" + ds.Tables[0].Rows[i]["CompletedBy"] + "</td>");
                    htmlTable.Append("<td>" + ds.Tables[0].Rows[i]["DateCreated"] + "</td>");
                    htmlTable.Append("<td width=\"10%\"><button class=\"astext\" name=\"Btn" + ds.Tables[0].Rows[i]["CCPOF_ID"] + "\" id =\"" + ds.Tables[0].Rows[i]["CCPOF_ID"] + "\" OnClick =\"btnEdit_Click\" runat=\"server\" >Edit</button> | Details</td>");
                    htmlTable.Append("</tr>");
                }
                htmlTable.Append("</table>");
                DBDataPlaceHolder.Controls.Add(new System.Web.UI.WebControls.Literal { Text = htmlTable.ToString() });
            }
            else
            {
                htmlTable.Append("<tr>");
                htmlTable.Append("<td align='center' colspan='4'>There is no Record.</td>");
                htmlTable.Append("</tr>");
            }
        }
    }

    protected void btnEdit_Click(object sender, EventArgs e)
    {
        String id = ((System.Web.UI.WebControls.Button)sender).ID;
        Server.Transfer("CcpofDetails.aspx?ID=" + id);
    }
}

When I inspect the button in the live form this is what I see

<button class="astext" name="Btn10" id="10" onclick="btnEdit_Click" runat="server">Edit</button>

Ann L. · Answer 1 · 2016-08-12T19:25:33.337

I believe your problem comes from the fact that ASP.NET doesn't know you created a button. As far as it's concerned, all you did was pump out some text to the page.

As a result, when you post back to the server, it doesn't know it needs to do anything on the server side when you click.

Try creating it as an object (a System.Web.UI.WebControls.Button) and adding that to your page's Controls collection. Be aware that you'll have to do this both on the initial page build and on postback: if the control doesn't exist after postback, events that were hooked up to it don't fire.

Getting it to appear in the middle of your table may require you to do your HTML table creation in some other way, such as building a WebControls Table object and adding that to your Controls collection.

score 1 · Accepted Answer · answered Aug 12 '16 at 19:26

Your way of generating dynamic controls seems very strange to me. It is not the way web-forms work.

To run an event on a control, it has to be loaded into servers memory first. But you are just filling some html text that is understandable only for the browser, not for asp.net engine.

take a look at this sample

To give you a better idea, create your buttons like this

private void Page_Load(object sender, System.EventArgs e)
{
    if (!IsPostBack)
        AddControls();
}

protected override void LoadViewState(object savedState)
{
    base.LoadViewState(savedState);
    if (ViewState["controsladded"] == null)
    AddControls();
}

private void AddControls()
{
    TextBox dynamictextbox = new TextBox();
    dynamictextbox.Text = "(Enter some text)";
    dynamictextbox.ID = "dynamictextbox";
    Button dynamicbutton = new Button();
    dynamicbutton.Click += new System.EventHandler(dynamicbutton_Click);
    dynamicbutton.Text = "Dynamic Button";
    Panel1.Controls.Add(dynamictextbox);
    Panel1.Controls.Add(new LiteralControl("<BR>"));
    Panel1.Controls.Add(new LiteralControl("<BR>"));
    Panel1.Controls.Add(dynamicbutton);
    ViewState["controlsadded"] = true;
}

private void dynamicbutton_Click(Object sender, System.EventArgs e)
{
    TextBox tb = new TextBox();
    tb = (TextBox) (Panel1.FindControl("dynamictextbox"));
    Label1.Text = tb.Text;
}

So in terms that I can understand so i can grasp what you are saying, controls are only recognized if they are created at "compile-time" ( I don't know the web dev equivalence) or added via asp.net. Thus injecting anything into the html doc cannot communicate with asp.net? — Javant, Aug 12 '16 at 19:33
@Javant Yes, you are right. You cannot work with server-side code like that. — Ashkan S, Aug 12 '16 at 19:36
@Javant just to mention that you can work with Javascript code this way since it will run on the client side. But their task is totally different — Ashkan S, Aug 12 '16 at 19:37

score 0 · Answer 3 · edited May 23 '17 at 12:14

0

You are not adding corectl the button to the web form. Try this way:

Button btnEdit = New Button();
btn.Edit.Click += btnEdit_Click;
frmMain.Controls.Add(btnSave)

As shown in this question too.

edited May 23 '17 at 12:14

Community

1
1

answered Aug 12 '16 at 19:18

meJustAndrew

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Just makes the button(s) disappear – Javant Aug 12 '16 at 19:21
@Javant never happened to me before, let me check. Are you sure it is a asp.net webforms project? – meJustAndrew Aug 12 '16 at 19:24

Dynamically Created Button refuses to call it's onClick

3 Answers3