How to Dynamically create textboxes using ASP.NET and then save their values in Database?

Question

I am creating a survey site. I want to add the textboxes dynamically and then get their values in the database.

Now let's say I select 4 textboxes from the dropdown to be there dynamically.

Code on the Selection on dropdown :

     protected void NumDropDown_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (DropDownList1.SelectedValue == "TextBox")
        {

            int j;
            i = int.Parse(NumDropDown.SelectedValue);
            Session["i"] = i;
            switch (i)
            {
                case 1:
                    t = new TextBox[i];
                    Session["textBox"] = t;
                    for (j = 0; j < i; j++)
                    {
                        t[j] = new TextBox();
                        t[j].ID = "txtCheckbox" + j.ToString();
                        Panel1.Controls.Add(t[j]);

                    }
                    break;
                case 2:
                    t = new TextBox[i];
                    Session["textBox"] = t;
                    for (j = 0; j < i; j++)
                    {
                        t[j] = new TextBox();
                        t[j].ID = "txtCheckbox" + j.ToString();
                        Panel1.Controls.Add(t[j]);

                    }
                    break;

                case 3:
                    t = new TextBox[i];
                    Session["textBox"] = t;
                    for (j = 0; j < i; j++)
                    {
                        t[j] = new TextBox();
                        t[j].ID = "txtCheckbox" + j.ToString();
                        Panel1.Controls.Add(t[j]);

                    }
                    break;
                case 4:
                    t = new TextBox[i];
                    List<TextBox> MyTextBoxes;
                    for (j = 0; j < i; j++)
                    {
                        t[j] = new TextBox();
                        t[j].ID = "txtCheckbox" + j.ToString();
                        Panel1.Controls.Add(t[j]);
                        try
                        {
                            MyTextBoxes = (List<TextBox>)Session["AddedTextBox"];
                            MyTextBoxes.Add(t[j]);
                            Session["AddedTextBox"] = MyTextBoxes;
                        }
                        catch
                        {
                            MyTextBoxes = new List<TextBox>();
                            MyTextBoxes.Add(t[j]);
                            Session["AddedTextBox"] = MyTextBoxes;
                        }
                    }
                    break;
            }

        }
    }

2) Then Here I entered the values in the textBox like a, b,c,d and click ADD:

Code for the click On the ADD Click :

1) First i checked the session to be there on Page_Init :

    protected void Page_Init(object sender, EventArgs e)
    {
        if (Session["AddedTextBox"] != null)
        {
            string a;
            string b;
            string c;
            string d;

            int listCount = ((List<TextBox>)Session["AddedTextBox"]).Count;
            foreach (TextBox t in ((List<TextBox>)Session["AddedTextBox"]))
            {
                if (listCount == 1)
                {

                }
                if (listCount == 2)
                {

                }
                if (listCount == 3)
                {

                }
                if (listCount == 4)
                {
                    if (t.ID == "txtCheckbox0")
                    {
                        a = t.Text;
                    }
                    if (t.ID == "txtCheckbox0")
                    {
                        b = t.Text;
                    }
                    if (t.ID == "txtCheckbox0")
                    {
                        c = t.Text;
                    }
                    if (t.ID == "txtCheckbox0")
                    {
                        d = t.Text;
                    }

                }
            }
        }

But the problem here is that I don't get the text values, they Appear to be empty. Please help me to solve this issue.

Answer 1

As @jenson-button-event mentioned you can access the TextBox values through Request.Form here's an example:

ASPX:

<asp:DropDownList ID="ddlTextBoxes" runat="server">
    <asp:ListItem Value="1" Text="1" />
    <asp:ListItem Value="5" Text="5" />
</asp:DropDownList>
<asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="Add" /><br />
<asp:PlaceHolder ID="container" runat="server" Visible="false">
    <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="Submit" />
</asp:PlaceHolder>

Code behind:

    protected void Add(object sender, EventArgs e)
    {
        int numOfTxt = Convert.ToInt32(ddlTextBoxes.SelectedItem.Value);
        var table = new Table();

        for (int i = 0; i < numOfTxt; i++)
        {
            var row = new TableRow();
            var cell = new TableCell();

            TextBox textbox = new TextBox();
            textbox.ID = "Textbox" + i;
            textbox.Width = new Unit(180);

            cell.Controls.Add(textbox);
            row.Cells.Add(cell);
            table.Rows.Add(row);
        }

        container.Controls.AddAt(0,table);
        container.Visible = true;
    }

    protected void Submit(object sender, EventArgs e)
    {
        var textboxValues = new List<string>();
        if (Request.Form.HasKeys())
        {
            Request.Form.AllKeys.Where(i => i.Contains("Textbox")).ToList().ForEach(i =>
                {
                    textboxValues.Add(Request.Form[i]);
                });
        }

        //Do something with the textbox values
        textboxValues.ForEach(i => Response.Write(i + "<br />"));
        container.Visible = false;
    }

Answer 2

This sounds like the age-old classic problem with asp.net adding controls dynamically to a page.

The problem is to with viewstate and reconstruction of the controls on postback.

You need to run the same code that generated the controls on postback at the correct time in the page lifecycle to ensure postback values match server-side controls.

Of course if you want a hacky shortcut, access the Request.Form["textCheckbox" + index] values directly

A useful article on the subject.