In C#, why is String a reference type that behaves like a value type?

c# string clr value-type reference-type
Davy8 picture Davy8 · Mar 12, 2009 · Viewed 176.7k times · Source

A String is a reference type even though it has most of the characteristics of a value type such as being immutable and having == overloaded to compare the text rather than making sure they reference the same object.

Why isn't string just a value type then?

Answer

codekaizen picture codekaizen · Mar 12, 2009

Strings aren't value types since they can be huge, and need to be stored on the heap. Value types are (in all implementations of the CLR as of yet) stored on the stack. Stack allocating strings would break all sorts of things: the stack is only 1MB for 32-bit and 4MB for 64-bit, you'd have to box each string, incurring a copy penalty, you couldn't intern strings, and memory usage would balloon, etc...

(Edit: Added clarification about value type storage being an implementation detail, which leads to this situation where we have a type with value sematics not inheriting from System.ValueType. Thanks Ben.)

Related questions

How can I convert String to Int?

I have a TextBoxD1.Text and I want to convert it to an int to store it in a database. How can I do this?

Read More
Convert int to string?

How can I convert an int datatype into a string datatype in C#?

Read More
Converting string to byte array in C#

I'm converting something from VB into C#. Having a problem with the syntax of this statement: if ((searchResult.Properties["user"].Count > 0)) { profile.User = System.Text.Encoding.UTF8.GetString(searchResult.Properties["user"][0]); } I then see the following errors: Argument 1: cannot …

Read More