Dynamic Buttons won't hold value after Post Back

Question

I have buttons that display dynamically when the page loads. What is suppose to do is:

1. Click a dynamic button, displays to a text box
2. Click Issue Ticket
3. Print Ticket 1.

If I click on the next dynamic button it should go thru the same process and it should print Ticket 2.

The issue is that is not incrementing in value. I believe is because the page postback everytime I click the Issue Ticket therefore resetting the ticket value back to 1. Anyway to go around this.

int ticket = 0;    

protected void Page_Load(object sender, EventArgs e)
{
      string buttonName;
      try
      {

         btnIssueTicket.Enabled = false;
         using (SqlConnection connStr = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectString"].ConnectionString))
           {
                connStr.Open();
                SqlCommand select = new SqlCommand("SELECT TransTypeId, TransTypeDesc from tblTransType", connStr);
                SqlDataReader reader = select.ExecuteReader();

                //Reads all records 
                while (reader.Read())
                {
                    transID = Convert.ToInt32(reader["TransTypeId"].ToString());
                    buttonName = reader["TransTypeDesc"].ToString();

                    CreateButton(buttonName);
                }

                connStr.Close();
                reader.Close();

            }
        }
        catch (Exception ex)
        {
            lblStatus.Text = "Error: " + ex.Message.ToString();
        }

    } 
}

 //Buttons properties. Creates buttons dynamically inside the Layout Panel
    private void CreateButton(string buttonName)
    {


        transbutton = new Button();

        transbutton.Text = buttonName;
        transbutton.ID = transID.ToString();
        transbutton.CssClass = "transButtons";  //CSS property for buttons        
        transbutton.Click += new EventHandler(transbutton_Click); //Event Handler for dynamic buttons
        panelButtons.Controls.Add(transbutton); //Adds button to Layout Panel

    }

    //When Dynamic buttons clicked.
    private void transbutton_Click(object sender, EventArgs e)
    {  
        //Displays Transactions in TextBox
        tbList.Text += ((Button)sender).Text + "\r\n";
        btnIssueTicket.Enabled = true;
        lblStatus.Text = "";                   
    }

   protected void btnIssueTicket_Click(object sender, EventArgs e)
    {

         tbPrint.Text = ticket + 1;
    }

Answer 1

You need to have ID for a control if it is created dynamically.

Otherwise, they will become null when the page is posted back to server.

rotected void Page_Load(object sender, EventArgs e)
{
   string buttonName;
   try
   {   
      ...
      CreateButton(transID, buttonName); // Pass transID          
      ...
   } 
}

private void CreateButton(int transID, string buttonName)
{
  transbutton = new Button();
  transbutton.Text = buttonName;
  transbutton.ID = transID.ToString(); // ID is required
  ...
}

Besides, if you want to keep track the number of tickets, you need to save it in ViewState to persist the data.

public int Ticket
{
    get { return Convert.ToInt32(ViewState["Ticket"] ?? 0); }
    set { ViewState["Ticket"] = value; }
}

// Usage
protected void btnIssueTicket_Click(object sender, EventArgs e)
{
     Ticket++;
     tbPrint.Text = Ticket.ToString();
}

Answer 2

Since you having integer value as tbPrint.Text You can do as below

Set initial tbPrint.Text 1 and

int no;
if (int.TryParse(tbPrint.Text, out no))
{
    tbPrint.Text = no + 1;
}

Otherwise You can use Session, Viewstate, or a hidden field.

Answer 3

When you declare a variable inside your page class, it is initialized to its value every time a request hits the server.

So each time, your ticket value is initialized to 0.

If you want to keep this value over multiple requests, you should use the ViewState and keep that value in it.

The ViewState will be rendered as a hidden field and sent back to the server at every postback, and you'll be able to keep the precedent value.

To have a better understanding of which values are kept and which are lost, take a look at the asp.Net page lifecycle: http://msdn.microsoft.com/en-us/library/ms178472(v=vs.80).aspx

and also there is a very complete description of the viewstate here: http://msdn.microsoft.com/en-us/library/ms972976.aspx

and also here: http://www.codeproject.com/Articles/31344/Beginner-s-Guide-To-View-State