title: How to modify the set value of update command npgsql postgresql c#
body: <p>i've been trying to modify an sql command for postgresql on c#. The line in comment quotes is the one working, but i need to change the set from pre-defined to variable. Although after 
  using the same way to define it as a variable, with a text given by the user on another form, it doesnt seem to work. Which is the correct way to replace the "first_name" with a variable ?</p>
  
  <pre><code>   String oldname = Actor.oldname;
  String newname = Actor.newname;
  String column = Actor.columnname;
  
  try
      {
          string connstring = "Server=127.0.0.1; Port=5432; User Id=postgres; Password=72677267; Database=imdb;";
  
          NpgsqlConnection connection = new NpgsqlConnection(connstring);
  
          connection.Open();
  
          //NpgsqlCommand command = new NpgsqlCommand("UPDATE actor SET first_name = " + newname + " WHERE first_name =" + oldname + "", connection);
  
          NpgsqlCommand command = new NpgsqlCommand("UPDATE actor SET " + column + " = " + newname + " WHERE " + column + " =" + oldname + "", connection);
  
          NpgsqlDataReader dataReader = command.ExecuteReader();
  
          connection.Close();
  
           return dataItems;
      }
  catch (Exception msg)
      {
          MessageBox.Show(msg.ToString());
          throw;
      }
  </code></pre>