How to get dynamically created textbox value

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Hi,
I want to get dynamically created textbox value in asp.net

This is code which I have created in this code text box are created but when I will input the value in the text and retrieve the value from dynamically created text box it give error
Object reference not set to an instance of an object

Below is my code...

protected void Page_Init(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //Generate initial textboxes 
            GenerateButton_Click(sender, e);
        }
    }
    protected void GenerateButton_Click(object sender, EventArgs e)
    {
        //Generate textboxes 
        int z = int.Parse(HowManyToGenerateTextBox.Text);

        Panel1.Controls.Clear();

        for (int i = 0; i < z; i++)
        {
            TextBox s = new TextBox();
            s.ID = "tb" + i.ToString();
            Session[s.ID] = s;
            Panel1.Controls.Add(s);
        }
    }
    protected void CalculateButton_Click(object sender, EventArgs e)
    {
        //Calculate sum 
        int sum = 0;

        for (int i = 0; i < Session.Count; i++)
        {
            TextBox txt = (TextBox)Panel1.FindControl("tb" + i.ToString());
            ResultLabel.Text = txt.Text;

           
            if (ResultLabel.Text != null)
                sum += int.Parse(ResultLabel.Text);
        }

        ResultLabel.Text = sum.ToString();
    }

Posted 17-Dec-14 23:54pm

basurajkumbhar

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Comments

Praveen Kumar Upadhyay 18-Dec-14 6:02am

By seeing your code I can say that if there will be a postback, you will loose all your dynamic created controls.

basurajkumbhar 18-Dec-14 6:09am

When I click on the Generate Button then TextBox are created and when i click on the Calculate Button then
TextBox txt = (TextBox)Panel1.FindControl("tb" + i.ToString());
Here in the txt the vale is null,
ResultLabel.Text = txt.Text;
at this line line i am getting the error

Object reference not set to an instance of an object

What i want to do in my code to get the text value.

3 solutions

Solution 3

try this,

TextBox txt = (TextBox)Panel1.FindControl("tb" + i);

or

may be this link could help you:

http://stackoverflow.com/questions/12560074/handle-dynamic-control-in-asp-net-findcontrol[^]

Posted 18-Dec-14 1:32am

deepankarbhatnagar

Comments

basurajkumbhar 18-Dec-14 7:54am

Thank's fro giving this help full link
Deepak....

deepankarbhatnagar 18-Dec-14 7:57am

your welcome

Solution 1

In your code, it is written that GenerateTextBox when there is no post back. When you will click on Calculate button so your complete page will be postback and your dynamic controls will be lost, So you need to retain the dynamic controls.

Check out below link, It will definitely solve your problem.

Retaining State for Dynamically Created Controls in ASP.NET applications[^]

Posted 18-Dec-14 0:16am

Praveen Kumar Upadhyay

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Sid_Joshi · Accepted Answer · 2014-12-18T00:31:00

try this

C#

protected void Page_Load(object sender, EventArgs e)
    {
        if(Page.IsPostBack)
        GenerateButton_Click(sender, e);
    }
    public TextBox[] s;
    protected void GenerateButton_Click(object sender, EventArgs e)
    {
        int z = Convert.ToInt32(TextBox1.Text);
        Panel1.Controls.Clear();
        Array.Resize(ref s, z);
        for (int i = 0; i < z; i++)
        {
            s[i] = new TextBox();
            s[i].ID = "tb" + i.ToString();
            s[i].Text = "tb" + i.ToString();
            Session[s[i].ID] = s;
            Panel1.Controls.Add(s[i]);
        }
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
                Response.Write(s[0].Text);
    }