How do you ensure that the database connections are always closed? | ASP.Net interview questions

To ensure that the database connections are always closed, open the connection inside of a using block, as shown in the following code fragment. Doing so ensures that the connection is automatically closed when the code exits the block.
using (SqlConnectionConnectionObject = new SqlConnection())
{
ConnectionObject.Open();
//The database connection will be closed when the control exits the using code block
}