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This article mainly shows you "what you need to pay attention to when using CLR in C#", the content is simple and clear, and I hope it can help you solve your doubts. Let me lead you to study and learn this article "what you need to pay attention to when using CLR in C#".

1. Performance problems of foreach of C # CLR

The implementation of foreach (string s in rows) {foo (s);} is:

IEnumerator e = rows.GetEnumerator (); try {string s; while (e.MoveNext ()) {s = (String) e.Current; foo (s);}} finally {IDisposable d = e as IDisposable; if (d! = null) d.Dispose ();}

The e.MoveNext () and e.Current methods are called at each step; most of the time, it is entirely possible to optimize to a single call. Obviously, this has an impact on performance. Although foreach makes separate optimizations for arrays (compiled into for loops), this is worth noting.

So, how to do it faster?

For Collection such as List, we can use ForEach (Actionaction), FindAll (Predicatematch), ConvertAll (Converterconverter) and other methods. They are faster, but not all classes that implement IEnumerable provide them.

LINQ pursues compatiblity, not performance. Therefore, the implementation of LINQ completely adopts foreach. It's worth noting.

2. The implementation principle of yield of C # CLR.

The yield keyword is usually used when implementing an object that supports IEnumerable, so that when foreach traverses the object, it can lazy evaluation. For example:

Class MyCollection: IEnumerable {private string s;... Public IEnumerable GetEnumerator () {for (int item0; i2)

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