A better way to dispose objects

An often-overlooked feature of ASNA Visual RPG (AVR) is its BegUsing operation. This operation allows for a more streamlined use of objects that provide a Dispose method that must be called before the object instance goes out of scope.

An object needs a Dispose method when it needs to release resources (generally COM or other external resources). While you may need to provide a Dispose method in objects you create, it’s not likely. Dispose is necessary only when the object acquires and needs to release unmanaged resources.

While custom objects needing Dispose are rare, many .NET Framework intrinsic objects provide a Dispose method. For example, .NET Frameworks’s StreamWriter and its new ZipArchive object (that lets you programmatically zip and unzip files with .NET Framework), both provide a Dispose method that must be called before the object instance goes out of scope. Not calling Dispose on objects that need it can lead to out-of-memory and other unpredictable errors.

AVR’s BegUsing operation

Before AVR got BegUsing, this is how you would have used the StreamWriter object to effectively dispose it:

DclFld writer Type(System.IO.StreamWriter)         

Try
    writer =  File.CreateText("c:\users\roger\newfile1.txt")
    writer.WriteLine('Neil')
    writer.WriteLine('Young')
Finally 
    If writer <> *Nothing
        writer.Dispose() 
    EndIf 
EndTry 

BegUsing streamlines the code needed to perform the Dispose. Note how BegUsing dispatches the need for manually calling Dispose.

 
Try
    BegUsing writer Type(StreamWriter) +
                    Value(File.CreateText('c:\users\roger\newfile2.txt')) 
        writer.WriteLine('Neil')
        writer.WriteLine('Young')          
    EndUsing
Catch ex Type(System.Exception)
    // do something with the exception here.
EndTry 

You won’t need BegUsing often, but when you do it’s quite handy. Also, its presence makes it easier to translate C# examples to AVR.

BegUsing is intended only for objects that provide a Dispose method (and therefore implement the iDisposable interface). Don’t try to use it with AVR objects like disk files or DataGate DB connections that need a Close or Disconnect method. Continue to close those objects with their Close or Disconnect methods as you have been.