Disposing a StringBuilder object

问题:

How does one effectively dispose a StringBuilder object? If an user generates multiple reports in a single sitting, my app ends up using a huge amount of memory.

I've read in a few sites online that the follow may help:

StringBuilder sb = new StringBuilder(1000000);

// loop goes here adding lots of stuff to sb

exampleObject.Text = sb.ToString();

sb.Length = 0;

Does the last line really help? Any other way of dealing with this?

NB: This does not really stop my users from continuing to use the application. I'm just wondering if there is a way of avoiding redundant memory usage.

回答1:

No, a StringBuilder is a purely managed resource. You should just get rid of all references to it. Everything else is taken care of by the garbage collector:

StringBuilder sb = ...;
// ... do work
sb = null; // or simply let it go out of scope.

In .NET, there's no deterministic delete (like C++, where you free up memory allocated to a single object.) Only GC can free memory. By forfeiting all references to an object, you'll let GC be able to deallocate the object if it wants to. You can force a garbage collection by calling the System.GC.Collect method. However, it's not recommended to manipulate with GC unless you really know what you are doing. GC is smart. It's rarely beneficial to force it.

回答2:

If you are generating many reports, you could consider re-using a single StringBuilder instead of allocating a new one for each report.

回答3:

Unless the 'excessive memory usage' is a problem, I would leave it as it is and not worry about it.

.NET is in most cases smart enough to avoid doing a garbage collection if you have enough memory available.