Question 20466 in Mysql Question posted in
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c# How to button.Visible = true when string exists? – Mysql

I want to make visible a button, but only when a string exists. This is the way I thought, but I’m not seeing any change to my UI. Furthermore, the loop doesn’t exit, despite only returning a single result.

using (MySqlConnection con = new MySqlConnection(ConnStr))
{
    con.Open();
               
                
    string sqlCON = "SELECT CV_EXIST FROM DATA_NEURON.DM_CV WHERE DWH_CUSTOMER_KEY = '123321'";
    MySqlCommand cmd = new MySqlCommand(sqlCON con);
                
    using (MySqlDataReader rdr = cmd.ExecuteReader())
    {
        while (rdr.Read())   
        {
            var check = rdr.GetString(0);
                        
            if (check == "YES")
            {
                button_cv.Visible = true;
            }
            else
            {
                button_cv.Visible = false;
            }
        }
    }
}

Thank you and sorry for my english.

Tags:

2

Answers


  1. 0

    Please note, that in your current implementation button_cv doesn’t change its state when cursor is empty and while loop is not entered; another
    possible issues are (trailing) spaces ("YES ") and case ("yes", "Yes" etc.). If it is "doesn’t work" then I suggest something like this:

    using (MySqlConnection con = new MySqlConnection(ConnStr)) {
  con.Open();

  //DONE: please, keep SQL readable
  //DONE: parametrize the query or have a good reason not to do it  
  string sqlCON = 
     @"SELECT CV_EXIST  
         FROM DATA_NEURON.DM_CV 
        WHERE DWH_CUSTOMER_KEY = @Key";

  //DONE: do not forget to dispose IDisposable - using
  using (MySqlCommand cmd = new MySqlCommand(sqlCON, con)) {
    //TODO: you may want to change MySqlDbType type, to, say, MySqlDbType.Int32
    cmd.Parameters.Add("Key", "123321", MySqlDbType.VarString);

    // You don't need the entire cursor here, just the 1st record if it exists
    button_cv.Visible = "YES".Equals(
      cmd.ExecuteScalar()?.ToString()?.Trim(), 
      StringComparison.OrdinalIgnoreCase);
  }
}

    Here I’ve assumed that empty cursor means NO; if it is YES then all you need is to change a single line by adding ?? "YES":

      cmd.ExecuteScalar()?.ToString()?.Trim() ?? "YES",
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  2. 0

    this code has syntax error :

    MySqlCommand cmd = new MySqlCommand(sqlCON con);

    best way is write a method for recognize button visibility and use its :

    public static bool GetButtonVisibility()
{
    using (var con = new MySqlConnection("connection string"))
    {
        con.Open();
        var query = "SELECT CV_EXIST FROM DATA_NEURON.DM_CV WHERE DWH_CUSTOMER_KEY = '123321'";
        var cmd = new MySqlCommand(query, con);
        using (var rdr = cmd.ExecuteReader())
            return rdr.Read() && rdr.GetString(0) == "YES";
    }
}

    button_cv.Visible = GetButtonVisibility();
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