String intern pool and extension

In C #, if you write [csharp] string msg1 = "abc";, during compilation, it is converted to the following IL command and stored in metadata to [csharp] LdStr "abc". Then, if you define another [csharp] string msg2 = "abc ";, the compiler recognizes that "abc" already exists and calls this IL command to direct the reference msg1 to msg2, of course, if you use the new method, it must be a new instance, and this will not work. In addition, when adding or subtracting a string, because the string type is a constant reference type, it means that as long as you perform some operations on the string, a new instance is usually generated. For the string pool, string has a method [csharp] string. intrrn (string str), this method will find the string reference with the same str value in the string pool and return it. If you use this method, it can be said that it saves the memory space, but it is not good if you use it too much, because it will remain occupied and will not be released until the CLR ends, that is, it will always exist until your program ends.