问题
there are 2 examples of code: # 1
string str1 = "hello";
string str2 = str1; //reference to the same string
str1 = "bye"; //new string created
and # 2
string str3 = "hello";
string str4 = (string)str3.Clone();//reference to the same string
str3 = "bye";//new string created
looks like they are identical aren't they? so what is the benefit to use Clone()? can you give me an example when I cannot use code#1 but code#2 ?
回答1:
This is useful since string implements ICloneable, so you can create a copy of clones for a collection of ICloneable items. This is boring when the collection is of strings only, but it's useful when the collection contains multiple types that implement ICloneable.
As for copying a single string it has no use, since it returns by design a reference to itself.
回答2:
Not directly in answer to your question, but in case you are looking to actually clone a string, you can use the static string.Copy() method.
回答3:
.Clone() in the above code is the same as the simple assignment. Also, string is immutable, so it will copy on write in both cases.
.Clone() would be a lot more useful in cases, where you are using different types, that implement the same interface (in this case IClonable) as you would not be able to use a simple assignment, but could still cast the object returned by Clone() to ICloneable and assign that reference. For instance iterating through a generic collection with ICloneable elements.
来源：https://stackoverflow.com/questions/3465377/whats-the-use-of-string-clone