Question

I have this code:

 con.Open();
 cmd = new MySqlCommand(String.Format("SELECT concat(name,'|',lastname) FROM {0} WHERE ID= ?Parname;", ConfigSettings.ReadSetting("my_data")), con);
 cmd.Parameters.Add("?Parname", MySqlDbType.VarChar).Value = id_value;
 var tokens = ((String)cmd.ExecuteScalar()).Split('|');
 name = tokens[0];
 lastname = tokens[1];

This is working perfectly when I enter id value and when user is actually in database. But I got null exception when there is no such a user inside the database. I need to make this to write me a unknown user if he is not in the database.

Answer 1

If there’s no user with the given id, the return value of ExecuteScalar is DBNull.Value:

var result = cmd.ExecuteScalar();
if (result != DBNull.Value)
{
    var tokens = ((String)result).Split('|');
    name = tokens[0];
    lastname = tokens[1];
}
else
{
    name = "unknown";
    lastname = "user";  // or whatever
}