Access a textbox in C# that is created on fly

Question

My code generates an TextBox on the fly in C# (page_load function). Can I access it in the code later? It does give me compilation error and does not seem to work. Can someone verify ?

Code for additonal problem

aContent += "<table>";
aContent += "<tr><td>lablel </td><td style='bla blah'><input type='textbox' id='col-1' name='col-1'/></td></tr> ... 10 such rows here
</table>"

spanMap.InnerHtml = aContent;

The contents are rendered OK but recusrive iteration does not return the textbox. I am calling it like this

 TextBox txt = (TextBox)this.FindControlRecursive(spanMap, "col-1");
 // txt = (TextBox) spanMapping.FindControl("col-1"); this does not work too
 if (txt != null)
 {
      txt.Text = "A";
 }

Where's your code? Did you add it to the Page controls? Do you re-add it on each postback? — Steve Wellens, Nov 08 '11 at 16:57
I am asking if it is possible. I think the question explain it well. It is not my code btw, someone else wrote it. — TheTechGuy, Nov 08 '11 at 17:00
This is old question, but first of the "textbox" isn't textbox, it is html input. You should add the textbox, like Textbox nTxt = new Textbox(); nTxt.id = "col-1"; spanMap.Controls.Add(nTxt); — Alker, Sep 29 '14 at 06:55

James Johnson · Accepted Answer · 2011-11-08T19:05:16.890

2

Assuming that you're persisting it correctly, you should be able to access it in code-behind using the FindControl method. Depending on where the control is, you may have to search recursively through the control hierarchy:

private Control FindControlRecursive(Control root, string id)  
{  
    if (root.ID == id) 
    {  
        return root;  
    }  

    foreach (Control c in root.Controls)  
    {  
        Control t = FindControlRecursive(c, id);  
        if (t != null)  
        {  
            return t;  
        }  
    }  

    return null;  
}

Using FindControlRecursive:

TextBox txt = this.FindControlRecursive(Page.Form, "TextBox1") as TextBox;
if (txt != null)
{
    string text = txt.Text;
}

If you still can't find it using the above method, make sure that you're creating the control during after every postback, somwhere before Page_Load, like OnInit.

EDIT

I think you need to change the way you're adding content to the container. Instead of using a <span>, I would use a Panel, and instead of building markup, simply add controls to the panel in code-behind:

TextBox txt = new TextBox();
txt.ID = String.Format("txt_{0}", Panel1.Controls.Count);
Panel1.Controls.Add(txt);

edited Nov 08 '11 at 19:05

answered Nov 08 '11 at 16:59

James Johnson

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So I guess FindControl is my only way to acess it. I can not directly access it. @sylence below did mention adding a reference but that is not very clear. – TheTechGuy Nov 08 '11 at 17:03
Yes, you definitely need `FindControl` to access a dynamic control. You can't access it directly. – James Johnson Nov 08 '11 at 17:06
I tried this code but it did not work. My html is actually inside a span. `spanMap.InnerHtml = aContent;`. Inside there is a table and inside table is my textbox. Although you need to change `as Textbox` to `TextBox( ...)`, in the second block of code. – TheTechGuy Nov 08 '11 at 18:41
I'm confused... what's the problem? The above method shouldn't have any problem traversing the tree. – James Johnson Nov 08 '11 at 18:43
I have included additional code in the question. It just does not find any child element except one literalcontrol. Also I am using masterpage, if that makes any difference. I used it before though and it did work (not this particular example). – TheTechGuy Nov 08 '11 at 18:58
Oh, so you're not using an ASP.NET TextBox? Either use an ASP.NET TextBox or add `runat="server"` to the input element, and you should be able to find it. – James Johnson Nov 08 '11 at 19:02
I see, thanks for clearing this up! That's a big help. I am still work on it though. – TheTechGuy Nov 08 '11 at 19:12
I just provided a simple example, but you should be able to recreate your markup using the `Table`, `TableRow`, and `TableCell` controls, and obviously the `DropDownList` control. – James Johnson Nov 08 '11 at 19:15
Thank you a bunch for the help. While it still did not work, possible culprit is span. But I now know what is wrong. I was going to change the design anyways, there was no need to create this particular form on the fly. Thank you again – TheTechGuy Nov 08 '11 at 20:10
You're very welcome. Just let me know if you need any more help ;) – James Johnson Nov 08 '11 at 20:11

score 1 · Answer 2 · answered Nov 08 '11 at 17:05

Here's an example:

<%@ Page Language="C#" %>
<script type="text/C#" runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        var textBox = new TextBox();
        textBox.ID = "myTextBox";
        textBox.Text = "hello";
        Form1.Controls.Add(textBox);
    }

    protected void BtnTestClick(object sender, EventArgs e)
    {
        var textBox = (TextBox)Form1.FindControl("myTextBox");
        lblTest.Text = textBox.Text;
    }
</script>
<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>
    <form id="Form1" runat="server">
        <asp:LinkButton ID="btnTest" runat="server" Text="Click me" OnClick="BtnTestClick" />
        <asp:Label ID="lblTest" runat="server" />
    </form>
</body>
</html>

Access a textbox in C# that is created on fly

2 Answers2