.NET Tip: Managing Resources with the Using Statement

Last week, I showed you how you can help ensure that your objects release their resources by implementing IDisposable. This week, I want to show you the using statement that allows you to specify when your objects release their resources. Objects declared in the using statement will explicitly be disposed when the end of the using block is reached. I often use nested using statements for data access to precisely control the creation and disposal of my objects. Here is how you can take advantage of the using statement to create a database connection, create a command, and execute a data reader to access your data.

using (SqlConnection CN =
   new SqlConnection("*** Your connection string here ***"))
{
   CN.Open();
   using (SqlCommand cmd =
          new SqlCommand("SELECT * FROM authors", CN))
   {
      using (SqlDataReader dr = cmd.ExecuteReader())
      {
         // Access elements items here
      }
   }
}

By nesting the using statements above, you can be sure you are creating objects only when necessary and that, once everything is finished, your objects will all be disposed of in a timely manner. If an error should occur anywhere along the way, any objects created up to that point will still be disposed of when the using block is exited. The only caveat is that the object declared in the using statement must implement the IDisposable interface. Keep this in mind if you plan on taking advantage of the using statement with your own classes.

About the Author

Jay Miller is a Software Engineer with Electronic Tracking Systems, a company dedicated to robbery prevention, apprehension, and recovery based in Carrollton, Texas. Jay has been working with .NET since the release of the first beta and is co-author of Learn Microsoft Visual Basic.NET In a Weekend. Jay can be reached via email at jmiller@sm-ets.com.