Handle ASP.NET web service method exit

Question

Say I have a web service that works with a database. Each method opens the database, and then of course closes it on exit.

Is there any method to move the open/close code outside the web method itself? Something like OnBeforeWebMethodCalled / OnAfterWebMethodCalled.

So instead of

[WebMethod]
public void Hello()
{
   OpenDatabase();
   try { } finally { CloseDatabase(); }
}

we will have

private void OnBeforeWebMethodCalled() { OpenDatabase(); }
private void OnAfterWebMethodCalled() { CloseDatabase(); }
[WebMethod]
public void Hello()
{
  // the database is ready here
}

Thanks everybody for suggesting the using keyword but I know about it. The problem is that I have a legacy service of first kind and I'd like to easily wrap the database stuff to make it the second kind.

Now, imagine it's not a database stuff. Imaging I'd like to log web methods entry/exit. Or I want to send emails about which method is called. Whatever. What I really need is to execute some code at entry/exit of the web method. And I don't want to inject this code into every single web method. Ideally if I can catch exceptions, too.

Answer 1

This is a really really bad idea.

First off, your database access should be wrapped in a using statement. If you aren't going to do that, then the very least you need is a try catch.

Second, how would the web service runtime know whether you really needed to open a DB connection or not anyway?

Finally What if the db call blows up? What would your web method do to handle an orphaned connection? Or, what would the web method do if the open failed?

Answer 2

Have a private method that gets you an open database connection. Wrap your use of it in a using block, then it will be closed/disposed properly without you having to think about it.

private IDbConnection GetDbConn()
{
    SqlConnection conn = new SqlConnection("connectionstringhere");
    conn.Open();
    return conn;
}

[WebMethod]
public void SomeWebMethod()
{
    using (IDbConnection conn = GetDbConn())
    {
        // your code here
    }
}

Followup

I really don't see how you'll be able to catch exceptions without putting try {} catch {} in each of your web methods.

With regards to running something at the start and end of each web method, perhaps you could look at firing an event, to which methods would be hooked up in the constructor for your web service.

If you need to guarantee that the "end" event would be fired regardless of whether your web method threw an exception, put it in a finally {} block.

This would require you to edit each web method once to add the event code, but then you can add/remove event handlers as required from one central place (the constructor).

[WebService(Namespace = "http://YourWebServiceNamespace")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ToolboxItem(false)]
public class YourWebService : System.Web.Services.WebService
{
  private event EventHandler WebMethodStarted;
  private event EventHandler WebMethodCompleted;

  public YourWebService()
  {
     WebMethodStarted += new EventHandler(YourWebService_WebMethodStarted);
     WebMethodCompleted += new EventHandler(YourWebService_WebMethodCompleted);
  }

  [WebMethod]
  public void SomeWebMethod()
  {
      OnWebServiceStarted();

      try
      {
          // your code here
      }
      catch
      {
          // this is where I suggest you do your exception handling for each webmethod
      }
      finally
      {
          OnWebServiceCompleted();
      }
  } 


  private void OnWebMethodStarted()
  {
      if (WebMethodStarted != null)
          WebMethodStarted(this, EventArgs.Empty);
  }    

  private void OnWebMethodCompleted()
  {
      if (WebMethodCompleted != null)
          WebMethodCompleted(this, EventArgs.Empty);
  }    

  private void YourWebService_WebMethodStarted(object sender, EventArgs e)
  {
      throw new NotImplementedException(); // your code here
  }

  private void YourWebService_WebMethodCompleted(object sender, EventArgs e)
  {
      throw new NotImplementedException(); // your code here
  }
}

Answer 3

I stumbled upon a possible solution to this issue for you

http://www.postsharp.org/

Answer 4

You should use repository class that encapsulates open and close method within itself. In a way it is a bad practise to open and close database connection on front-ends.

public static class DBRepository
{

    public static void SomeOps(string args)
    {
        //open db
        //your ops
        //close db
    }

}

Call DBRepository.SomeOps from web-service.