[C#] using statement, where and how to use it

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In my app i am using streamreader, streamwriter, and so on. I would like to use using statement, because there is no need for .Close(), .Dispose(),... is that right? Using makes it for you? And that releases the memory?
What is the rule where and how to use using?

And one more thing: Let say that i have a code for streamreader and i forgot to use .Close(), where in Visual Studio can i see (while debuging) that i forgot it and that it uses memory,...

Posted 26-Mar-13 8:09am

marcel zol

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Thomas Daniels · Answer 1 · 2013-03-26T08:12:00

Solution 1

Hi,

Have a look at these articles about the 'using' statement:
Understanding the 'using' statement in C#[^]
The "using" Keyword in C#[^]
http://msdn.microsoft.com/en-us/library/yh598w02%28v=vs.110%29.aspx[^]

Posted 26-Mar-13 8:12am

Thomas Daniels

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Andreas Gieriet 26-Mar-13 18:32pm

My 5!
Cheers
Andi

Thomas Daniels 27-Mar-13 3:21am

Thank you!

PIEBALDconsult · Answer 2 · 2013-03-26T08:57:00

Solution 2

"there is no need for .Close(),"

The using statement will call Dispose, and Dispose will call Close (in most classes that have a Close), but I still call Close as a matter of discipline; there's no reason not to.

Posted 26-Mar-13 8:57am

PIEBALDconsult

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Andreas Gieriet 26-Mar-13 18:34pm

My 5!
Documentation on Dispose() is not always clear. You can assume to get (external) resources released at that point. The rest is "bonus" ;-)
Cheers
Andi

OriginalGriff · Answer 3 · 2013-03-26T11:27:00

Solution 3

To add to what PIEBALDconsult says, the other advantage of using using is that unlike Close or Dispose, it also limits the scope of the variable to the section of code in which it is valid.
Once you leave the using block, the variable goes out of scope, which means that the compiler will complain if you try to use a variable which has been disposed.

[edit]Typo: "hours" for "goes" (tablet typing) - OriginalGriff[/edit]

Posted 26-Mar-13 11:27am

OriginalGriff

Updated 26-Mar-13 11:30am

v2

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Andreas Gieriet 26-Mar-13 18:36pm

My 5!
Just a small note: since the variable goes out-of-scope, the compiler will complain about unknown variable and not about already disposed object.
Cheers
Andi

OriginalGriff 27-Mar-13 4:43am

You are right - I should have phrased that better!

Andreas Gieriet · Answer 4 · 2013-03-26T11:35:00

To your second question: FxCop has rules to detect missing Dispose() calls.
Depending on your installed Visual Studio flawour, you might have FxCop rules directly available or you might need to run FxCop as a separate build step (e.g. as post build event).
Missing Close() calls go undetected, though, but if the missing Dispose() is detected, a missing Close() is irrelevant.
Cheers
Andi