Using 'using' in front of StreamWriter

Question

I'm doing a tutorial on how to save a text file with StreamWriter. I understand how to do it but I started reading a tutorial on the StreamWriter Class to get a better understanding of it. In an example, it places the word using StreamWriter but in the other tutorial, it does not. Why is this? Do I need to use the using?

how to save to text tutorials way

private void button3_Click(object sender, EventArgs e)
        {
            StreamWriter File = new StreamWriter("data.txt", true);

            File.Write("");
            File.Close();
        }

== StreamWriter Class In C# With Programming Example ==

namespace StreamWriter_Class
{
    class Program
    {
        static void Main(string[] args)
        {
            string file = @"D:\csharpfile.txt";
        --->    using (StreamWriter writer = new StreamWriter(file))

Using `Using` will allow for automatic garbage collection. See [this answer](https://stackoverflow.com/a/10057366/1350913) — IronAces, Dec 04 '18 at 16:54
Using is used for classes that implement IDisposable. It is the same as wrapping the block of code in a try/catch/finallyblock and running the .Dispose method in the 'finally' section. If you don't do this, it can cause memory leaks. Using is the preferred way of doing this. — Jon Vote, Dec 04 '18 at 16:54
Thank you for the quick responses. There are a lot of good tutorials out there, but they don't explain the little things like that too well or at all. — , Dec 04 '18 at 17:04
@DanielShillcock that is a mis-statement; `using` doesn't impact the garbage collection **at all**. Disposal is different to collection. — Marc Gravell, Dec 06 '18 at 09:06

score 2 · Answer 1 · answered Dec 04 '18 at 16:56

using is a syntactic sugar that makes sure that the resource you are using (no pun intended!) will be Dispose()d , no matter if the actions that were performed on it threw any exception (which is not uncommon when handling external resources).

WHile it's not strictly "wrong" not to use it, it's a very good practice, and you should probably adopt it wherever possible.

See the official documentation for additional details.

score 1 · Answer 2 · edited Jun 20 '20 at 09:12

1

Every using will become something like that:

StreamWriter writer = new StreamWriter(file);
try
{
    // do something with writer
}
finally
{
    if(writer != null)
        writer.Dispose(); // close handle and free resorces
}

Always your writer handle and resources will be closed and free and GC don't need to check that.

You can use using in yours own classes implementing IDisposable interface.

See:

https://www.dotnetperls.com/using

When should I use "using" blocks in C#?

Implementing IDisposable correctly

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/try-catch-finally

edited Jun 20 '20 at 09:12

Community

1
1

answered Dec 04 '18 at 16:58

Kevin Kouketsu

786
6
20

Close, except the variable is declared outside the try so that it has scope in the finally... – michael Dec 04 '18 at 17:01
Yes, you're right @michael. Edited – Kevin Kouketsu Dec 04 '18 at 17:02
Close again, the assignment is done in the try... but the declaration is done outside. – michael Dec 04 '18 at 19:19

score 1 · Answer 3 · answered Dec 04 '18 at 17:00

using will make sure that the object (in this case StreamWriter) will be disposed, when it is out-of-scope.

There are posted plenty of examples with explanations in this question: What are the uses of "using" in C#?

And here is a really good explanation from DotNetPerls: DotNetPerls - Using

Using 'using' in front of StreamWriter

3 Answers3