What's the use of System.String.Copy in .NET?

Question

I\'m afraid that this is a very silly question, but I must be missing something.

Why might one want to use String.Copy(string)?

The documentation says the me

Answer 1

I am not sure how String being implemented in .NET, but I think Java is a good reference.

In Java, new String(str) also do what String.copy(str); do, allocate a new String with same value.

It seem useless but it is very useful in memory optimization.

String contains a char[] with offset and length in the implementation. If you do a something like a substring, it won't do a memory copy but return a new String instance sharing same char[]. In many cases, this pattern will save a lot of memory copy and allocation. However, if you substring a small piece within a long large String. It will still reference to large char[] even the original large String is able to be GC.

String longString = // read 1MB text from a text file
String memoryLeak = largeString.substring(100,102); 
largeString=null;
// memoryLeak will be sized 1MB in the memory
String smaller = new String(largeString.substring(100,102));
// smaller will be only few bytes in the memory

It can force the new String object allocate it's own char[] to prevent hidden memory leak/waste.