should I use isDbNull? How to use it in this particular case?

Question

I know Null values can't be turned into string values so I looked all over the web and did find some answers like using IsDBNull() but I can't seem to get it working. I'm new at this so please bear with me. I simply need the nullable field to be populated in the proper TextBox as "" when it's Null. If you could give me a hand with the proper syntax it would be great. the field that may be Null (or not) is projects_project_number, I went back to my original code to show what I started with. Here it is:

ConnectionStringSettings conSettings = ConfigurationManager.ConnectionStrings["shopmanagerConnectionString1"];
MySqlConnection con = new MySqlConnection(conSettings.ToString());
string Query = "select * from shopmanager.quotes where idquotes = @search_quote_number;";

MySqlCommand cmdDataBase = new MySqlCommand(Query, con);
MySqlDataReader myReader;
try
{
    con.Open();

    cmdDataBase.Parameters.AddWithValue("@search_quote_number", search_quote_number.Text);
    myReader = cmdDataBase.ExecuteReader();

    while (myReader.Read())
    {
        string sClient_number = myReader.GetString("client_info_client_number");
        string sId = myReader.GetInt16("idquotes").ToString();
        string sClientName = myReader.GetString("client_name");
        string spredicted_start_date = myReader.GetString("predicted_start_date");
        string sdate_required = myReader.GetString("requested_date");
        string sdate_predicted = myReader.GetString("delivery_expected_date");
        string sdate_received = myReader.GetString("date_received");
        string squote_amount = myReader.GetString("quote_amount");
        string sproject_number = myReader.GetString("projects_project_number");

        quote_id.Text = sId;
        client_name.Text = sClientName;
        predicted_start_date.Text = spredicted_start_date;
        date_required.Text = sdate_required;
        date_predicted.Text = sdate_predicted;
        date_received.Text = sdate_received;
        quote_amount.Text = squote_amount;
        project_number.Text = sproject_number;

        temp_client_id.client_id = sClient_number;
        search_quote_number.Text = "";
    }
    cmdDataBase.Parameters.Clear();
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}
con.Close();

Answer 1

To use the DBNull follow the guidance on MSDN about Is.DBNull()

There is multiple ways to use the DBNull but using what you have gave in your question, the best use would be:

string sproject_number = string.Empty;

if (!Convert.IsDBNull(myReader.GetString("projects_project_number"))) //check if value is not null
        sproject_number = myReader.GetString("projects_project_number"); 

project_number.Text = sproject_number;

You can also use the built in function for the SqlDataReader .IsDBNull:

int columnIndex = myReader.GetOrdinal("projects_project_number"); //get column index
string sproject_number = string.Empty;

if (!myReader.IsDBNull(columnIndex)) //check if value is not null
        sproject_number = myReader[columnIndex].ToString(); 

project_number.Text = sproject_number;

and for completeness:

int columnIndex = myReader.GetOrdinal();
string sproject_number = string.Empty;

if (DBNull.Value.Equals(myReader.GetString("projects_project_number"))) //check if value is not null
        sproject_number = myReader.GetString("projects_project_number");

project_number.Text = sproject_number;

Evaluating on a comment on original post about assigning to the textboxes directly and tidying everything up (and adding it into a using block is good practice):

ConnectionStringSettings conSettings = ConfigurationManager.ConnectionStrings["shopmanagerConnectionString1"]
string Query = "select * from shopmanager.quotes where idquotes = @search_quote_number;";
using(MySqlConnection con = new MySqlConnection(conSettings.ToString()))
{
  using(MySqlCommand cmdDataBase = new MySqlCommand(Query, con))
  {
    cmdDataBase.Parameters.AddWithValue("@search_quote_number", search_quote_number.Text.Trim());
    con.Open();
    var myReader = cmdDataBase.ExecuteReader();

    if(myReader.Read())
    {
      temp_client_id.client_id = myReader.GetString("client_info_client_number");
      quote_id.Text = myReader.GetInt16("idquotes").ToString();
      client_name.Text = myReader.GetString("client_name");
      predicted_start_date.Text = myReader.GetString("predicted_start_date");
      date_required.Text = sdate_required = myReader.GetString("requested_date");
      date_predicted.Tex = myReader.GetString("delivery_expected_date");
      date_received.Text = myReader.GetString("date_received");
      quote_amount.Text = myReader.GetString("quote_amount");
      project_number.Text = DBNull.Value.Equals(myReader.GetString("projects_project_number")) ? "" : myReader.GetString("projects_project_number");

      search_quote_number.Text = "";
    }
  }
}

Answer 2

You can do this:

string sproject_number = DBNull.Value.Equals(myReader.GetString("projects_project_number")) ? "" : myReader.GetString("projects_project_number");

Or you can use an extension method like in this SO Post: