Enable Textbox on SelectedIndex change

Question

I am grabbing some records from a database depending on the id number of the page, the amount of records that will display will vary, anywhere to 1 record to 50. I need to take these records then choose which ones I will be modifying, deleting, or won't change at all. I would like it to look like this:

Can't get image to show with stackoverflow image uploader so here: https://dl.dropboxusercontent.com/u/9446763/code/dropdownlist.jpg

I would like the text fields to be disabled if No Change or Remove is selected, and the fields enabled for revising if the option Modify is selected.

Below is what I have so far, the part I am struggling on is the selectedindex change I do not know how to code it so that when Modify is selected in the dropdown box the appropriate textboxes become enabled.

ASPX Page

<asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>

CS Page

private void createControls()
    {
        var id = Request.Params["ID"];
        System.Data.OleDb.OleDbConnection pcn;
        System.Data.OleDb.OleDbCommand pcm;
        System.Data.OleDb.OleDbDataReader prs;
        pcn = new System.Data.OleDb.OleDbConnection("");
        pcm = new System.Data.OleDb.OleDbCommand();
        pcn.Open();
        pcm.Connection = pcn;
        var tableSql = @"select * FROM grouplist where ptid = '" + id + "'";
        pcm.CommandText = tableSql;
        prs = pcm.ExecuteReader();
        var rowcount = 0;
        while (prs.Read())
        {
            rowcount++; 

            PlaceHolder1.Controls.Add(new Literal() { Text = "<div class='row'><div class='span3'>" });

            TextBox tx = new TextBox();
            tx.ID = "txtData" + rowcount.ToString();
            tx.Text = prs["name"].ToString().Trim();
            tx.Width = 200;
            tx.CssClass = "span2";
            tx.Enabled = false;
            PlaceHolder1.Controls.Add(tx);

            PlaceHolder1.Controls.Add(new Literal() { Text = "</div><div class='span2'>" });

            TextBox txa = new TextBox();
            txa.ID = "amtData" + rowcount.ToString();
            txa.Text = prs["amt"].ToString();
            txa.CssClass = "span2";
            txa.Enabled = false;
            PlaceHolder1.Controls.Add(txa);

            PlaceHolder1.Controls.Add(new Literal() { Text = "</div><div class='span3'>" });

            DropDownList ddl = new DropDownList();
            ddl.Items.Add("No Change");
            ddl.Items.Add("Modify");
            ddl.Items.Add("Remove");
            ddl.Width = 200;
            ddl.CssClass = "span2";
            ddl.SelectedIndexChanged += new EventHandler(ddl_SelectedIndexChanged);
            ddl.AutoPostBack = true;
            ddl.ID = "ddlData" + rowcount.ToString();

            PlaceHolder1.Controls.Add(ddl);

            PlaceHolder1.Controls.Add(new Literal() { Text = "</div></div>" });

        }
        prs.Close();
    }
  void ddl_SelectedIndexChanged(object sender, EventArgs e)
    {

    }

Answer 1

You need to have members in your class that hold references to your DropDownList and other controls that you want to enable/disable.

public class YourClass {
    private DropDownList ddl;
    private TestBox txa;

    private void createControls {
        // ...
        TextBox txa = new TextBox();
        txa.ID = "amtData" + rowcount.ToString();
        // ...
        DropDownList ddl = new DropDownList();
        ddl.Items.Add("No Change");
        // ... etc.
    }

    void ddl_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (ddl.SelectedIndex == 1)
            txa.Enabled = true;
    }
}