using System.Data.SqlClient; SqlConnection con = new SqlConnection("Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;"); SqlCommand cmd = new SqlCommand("SELECT Column1, Column2, Column3 FROM MyTable", con); con.Open(); SqlDataReader reader = cmd.ExecuteReader(); while (reader.Read()) { double value = reader.GetDouble(0); // Get the value of the first column as double Console.WriteLine(value); } reader.Close(); con.Close();In this example, we are querying a database table "MyTable" and retrieving the values of three columns using the SqlDataReader, and then printing the value of the first column as a double to the console. Package/Library: System.Data.SqlClient.