How does System.String save its string [closed]

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Closed 8 years ago.

To become better at .NET I found it helpful to look into the .Net-Framework itself and how Microsoft implements all the nice things. The last time I used my decompiler to have a look at the implementation of System.String-Class, to research how a String-Object stores its actual string. I was surprised about the largest of the class in self and that I can't clearly identify which part of the class the actual string saves.

Here are two screenshot of the decompiling which shows the start and the end part of the class:

I suppose that [System.Reflection.DefaultMember("Chars")] (first line in first screenshot) and/or the property public extern char this[int index](middle of second screenshot) the what I am looking for.

Is that the correct and if yes how does it work?

Answer 1

System.String is a very special type. It's the only type in .NET other than arrays where different instances can have different sizes. (Anything else which "appears" to have different sizes such as List<T> usually depends on an array, or some recursive type like a LinkedList node. The objects themselves are of a fixed size.) The character data is inline within the object itself, along with the length of the string. It's not like a String holds a reference to a char[] or similar.

The CLR has very deep knowledge of System.String, and a lot of it is implemented in native code. Basically, I would recommend against trying to understand the implementation at this point - it's likely to be more confusing than helpful.

The Chars member (the indexer in C#) only fetches a single character from the string. You could follow that to find out more about where the data is stored, but it doesn't perform the actual storage itself.