ASP.NET dynamically created textbox doesn't change value

Question

I have the following issue: I create a TextBox dynamically in my web page, its value is "initialVal" in the beginning. Now I need to make a postback (not callback) to the server, and during this operation, I need to compute/change the value of my textbox to other value.

Here's an example:

protected void Page_Load(object sender, EventArgs e)
    {
        TextBox txtBox = new TextBox();
        txtBox.ID = "newButton";
        form1.Controls.Add(txtBox);
        txtBox.Text = "initialVal";

        if (IsPostBack && Session["change"] == null)
        {
            txtBox.Text = "change";
            Session["change"] = true;
        }
    }

The problem: even if I change the value via code, the textbox will keep the text "initialVal". I feel this is something related to the view state, but I don't understand. Coudl anyone please help me here?

Thanks.

Better if you create it in Init event.

Morcilla de Arroz
– Morcilla de Arroz

2016-02-02 12:45:37 +00:00
Commented Feb 2, 2016 at 12:45 — Morcilla de Arroz
– Morcilla de Arroz, Commented Feb 2, 2016 at 12:45

NikolaiDante · Accepted Answer · 2016-02-02 13:32:03Z

1

Everytime you load the page it is running this:

txtBox.Text = "initialVal";

You should wrap this in a check for postback:

if (!Page.IsPostback)
{
    txtBox.Text = "initialVal";
}

That said, onLoad is the wrong event to do the creation, for it to be valid in the early enough in the page lifecycle, use OnInit.
See this article on MSDN.

Here is the final code from @user2890888:

public partial class WebForm1 : System.Web.UI.Page 
{ 
  TextBox txtBox = null; 

  protected void Page_Init(object sender, EventArgs e) 
  { 
    txtBox = new TextBox(); 
    txtBox.ID = "newButton"; 
    form1.Controls.Add(txtBox); 
  } 

  protected void Page_Load(object sender, EventArgs e) 
  { 
     if (!IsPostBack) 
     { 
       txtBox.Text = "initialVal"; 
     } 

     if (IsPostBack && Session["change"] == null) 
     { 
       txtBox.Text = "change"; 
       Session["change"] = true; 
      } 
   } 
}

edited Feb 2, 2016 at 13:32

answered Feb 2, 2016 at 12:49

NikolaiDante

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2 Comments

mocotrah Over a year ago

thanks Nikolai, I will put the solution in the Question body.

NikolaiDante Over a year ago

@user2890888 I'll edit the answer and add it in so it is readable, if thats ok.

Muhammad Jawwad · Accepted Answer · 2016-02-02 12:48:36Z

1

Create your dynamic textbox creation in !IsPostBack

    protected void Page_Load(object sender, EventArgs e)
        {
if(!isPostBack){
            TextBox txtBox = new TextBox();
            txtBox.ID = "newButton";
            form1.Controls.Add(txtBox);
            txtBox.Text = "initialVal";
    }
            if (IsPostBack && Session["change"] == null)
            {
                txtBox.Text = "change";
                Session["change"] = true;
            }
        }

Thanks and let me know if your issue still pending

answered Feb 2, 2016 at 12:48

Muhammad Jawwad

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1 Comment

mocotrah Over a year ago

nope, first of all the txtBox will become a local variable inside the if, code will not compile. Second, even if I get out of "if" the txtBox, it will be null. The TextBox must be created all the time, no only on !IsPostBack.

Tushar Gupta · Accepted Answer · 2016-02-02 12:48:51Z

0

Find the TextBox and use it

TextBox txtBox = (TextBox)FindControl("txtBox");
txtBox.Text = "change";

answered Feb 2, 2016 at 12:48

Tushar Gupta

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Comments

Rigin · Accepted Answer · 2016-02-02 12:56:56Z

0

Even now you are having issue and your textBox is not getting the value you needed. Store your new value for TEXTBOX in a hiddenfield. I mean ,

 if (IsPostBack && Session["change"] == null)
{
   hiddenfield1.value = "change";    
}

and later in your page script, you can assign back the value in this hiddenfield1 to textbox.

$(document).ready(
{
$('#txtBoxID').value=$('#hiddenfield1').value;
}
);

answered Feb 2, 2016 at 12:56

Rigin

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