create a 3rd party object
open a file handle
allocate some memory
open a database connection
open a network port
}
~MustDispose()
{
// customized destructor for this class
if (3rd party object != null)free the 3rd party object
if (file handle != null)close the file handle
if (memory != null)free the memory
if (connection != null) close the database connection
if (port open) close the network port
}
public void Dispose()
{
// because this class needs a destructor, it also needs this
// idiomatic Dispose method
Finalize();
System.GC.SuppressFinalize(this);
}
};
class NoDispose
{
public NoDispose()
{
// this class has an uninteresting constructor so it doesn't need
// a destructor or Dispose
}
MemberFuncThatCleansUp()
{
try
{
create a 3rd party object
open a file handle
allocate some memory
open a database connection
open a network port
}
finally
{
if (3rd party object != null)free the 3rd party object
if (file handle != null)close the file handle
if (memory != null)free the memory
if (connection != null) close the database connection
if (port open) close the network port
}
}
}
If a class needs a destructor, you should customize how it is written. However, the Dispose method has become an idiom in C# for any class that needs a destructor:
public void Dispose()
{
Finalize();
System.GC.SuppressFinalize(this);
}
When to Call Dispose
Call Dispose on an object you create if the class author provides Dispose. Call Dispose as soon as you are done using an object, especially if the object will remain in scope during a lengthy operation or if the object allocates significant resources of its own. If the object you create doesn't itself allocate significant resources (but how do you know that?) then it might not be a problem to simply let the object go out of scope and have C# call its destructor automatically.
Finally, here's a C# tip to actually avoid calling dispose:
MustDispose obj = new MustDispose;
try
{
// use the object
}
finally
{
if (obj != null)
((IDisposable)obj).Dispose();
}
You can shorten this up and just write this instead:
using (MustDispose obj = new MustDispose)
{
// use the object
}
This assumes that exceptions will be caught at a higher level, which is usually recommended. In other words, don't catch just to throw.
About the Author:
Scott Zimmerman is an award-winning .NET developer.
scottz1@hotmail.com
Read this Newsletter at: http://www.cprogrammingtrends.com/2004/0804.html |
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| From the Forum: |
| directing with MS Access |
| Hello, I took over a site that is password protected in certain areas. I saw a database on the site with a password list on it. Depending on the word you type in, it will take you to different sections of the site. I looks simple enough but when I try to get it to work, it doesn't. Does anyone have some help links for ASP? It looks like there are only two pages for this task, plus the database, which is in Access. ...
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By Scott Zimmerman
