Using

In this article The using statement ensures the correct use of an var numbers = new List(); using (StreamReader reader = File.OpenText("numbers.txt")) Warning In the preceding example, after control leaves the using statement, a disposable instance remains in scope while it's already disposed. If you use that instance further, you might encounter an exception, for example, using statement or with the using declaration. C# language specification For more information, see See also • • • • • • • • using directive

The reason for the using statement is to ensure that the object is disposed as soon as it goes out of scope, and it doesn't require explicit code to ensure that this happens. As in using (MyResource myRes = new MyResource()) C# 8 introduces a new syntax, named " A using declaration is a variable declaration preceded by the using keyword. It tells the compiler that the variable being declared should be disposed at the end of the enclosing scope. So the equivalent code of above would be: using var myRes = new MyResource(); myRes.DoSomething(); And when control leaves the containing scope (usually a method, but it can also be a code block), myRes will be disposed. Note that it's not necessarily a matter of the object being disposed correctly, but more of whether it is disposed in a timely manner. Objects implementing IDisposable which hold on to unmanaged resources like streams and file handles will also implement a finalizer that will ensure that Dispose is called during garbage collection. The problem is that GC might not happen for a relatively long time. using makes sure that Dispose is called once you're through with the object. Since a lot of people still do: using (System.IO.StreamReader r = new System.IO.StreamReader("")) using (System.IO.StreamReader r2 = new System.IO.StreamReader("")) Things like this: using (var conn = new SqlConnection("connection string")) This SqlConnection will be closed without needing to explicitly call the .Close() function, and this wil...

Usage Note: The verb use is used in the past tense with an infinitive to indicate a past condition or habitual practice: We used to live in that house. Because the -d in used has merged with the t of to and is not pronounced in these constructions, people sometimes mistakenly leave it out when writing. Thus it is incorrect to write We use to play tennis. When do occurs with this form of use in negative statements and in questions, the situation is reversed, and use to (not used to) is correct: You did not use to play on that team. Didn't she use to work for your company?

Verb I need to use the phone when you're done. The machine is easy to use. After the accident, she could no longer use her legs. We use only organic fertilizers on our farm. They make paper using traditional Japanese methods. He used his time there well. Which accountant do you use? a new kind of light bulb that uses very little electricity Did you use all the eggs? Who used the last match? Noun Two players were suspended for illegal drug use. Doctors have found a new use for the drug. According to the dictionary, the word has two uses. See More

Usage Note: The verb use is used in the past tense with an infinitive to indicate a past condition or habitual practice: We used to live in that house. Because the -d in used has merged with the t of to and is not pronounced in these constructions, people sometimes mistakenly leave it out when writing. Thus it is incorrect to write We use to play tennis. When do occurs with this form of use in negative statements and in questions, the situation is reversed, and use to (not used to) is correct: You did not use to play on that team. Didn't she use to work for your company?

The reason for the using statement is to ensure that the object is disposed as soon as it goes out of scope, and it doesn't require explicit code to ensure that this happens. As in using (MyResource myRes = new MyResource()) C# 8 introduces a new syntax, named " A using declaration is a variable declaration preceded by the using keyword. It tells the compiler that the variable being declared should be disposed at the end of the enclosing scope. So the equivalent code of above would be: using var myRes = new MyResource(); myRes.DoSomething(); And when control leaves the containing scope (usually a method, but it can also be a code block), myRes will be disposed. Note that it's not necessarily a matter of the object being disposed correctly, but more of whether it is disposed in a timely manner. Objects implementing IDisposable which hold on to unmanaged resources like streams and file handles will also implement a finalizer that will ensure that Dispose is called during garbage collection. The problem is that GC might not happen for a relatively long time. using makes sure that Dispose is called once you're through with the object. Since a lot of people still do: using (System.IO.StreamReader r = new System.IO.StreamReader("")) using (System.IO.StreamReader r2 = new System.IO.StreamReader("")) Things like this: using (var conn = new SqlConnection("connection string")) This SqlConnection will be closed without needing to explicitly call the .Close() function, and this wil...

Verb I need to use the phone when you're done. The machine is easy to use. After the accident, she could no longer use her legs. We use only organic fertilizers on our farm. They make paper using traditional Japanese methods. He used his time there well. Which accountant do you use? a new kind of light bulb that uses very little electricity Did you use all the eggs? Who used the last match? Noun Two players were suspended for illegal drug use. Doctors have found a new use for the drug. According to the dictionary, the word has two uses. See More

In this article The using statement ensures the correct use of an var numbers = new List(); using (StreamReader reader = File.OpenText("numbers.txt")) Warning In the preceding example, after control leaves the using statement, a disposable instance remains in scope while it's already disposed. If you use that instance further, you might encounter an exception, for example, using statement or with the using declaration. C# language specification For more information, see See also • • • • • • • • using directive