string is reference type or value type

Question

I am little confused whether a string datatype is reference type or a value type in C#. On googling, I found that string is a reference type but it behaves as a value type. Any simple example code to get me through this. Thanks

Sachin Singh · Answer

Yes, string is a reference type. But yes it behaves as a value type. That is why we say, that strings are immutable. Now, let's uunderstand it. Reference types means their values can be changed by changing the value at their location (address). example public class employee { public string Name; } employee emp1= new employee(); emp1.Name = "Sachin" ; employee emp2=emp1; emp2.Name= "Rohit" ; Now what will be emp1.Name ?? emp1.Name will be Rohit. because Complex types (class like employee here) are reference types, so when we changed the value at their refence , both gets changed. Value types:- Value types are those whose value doesn't change by reference. int x=10; int y=x; // y=10 x++; What will be the value of y now?? y will still be 10 but x will be 11. so, y doesn't change even if we changed the value of x. Now, come to string string x= "Sachin" ; string y=x; x= "Mohit" ; what will be the value of y ? it should be Mohit as it is reference type, but not, it will still be Sachin. But why ? what the heck wrong with string? String creates a new memory location each time a new value is assigned to it. so, the address are always different. so even if we change the value to its old address, it already went to a new address. string x= "Sachin" ; // address 1000 string y=x; // address still 1000 x= "Mohit" ; // since value changed so address changed now it is 1100 That is why we never use string concatination inside a loop, otherwise there will be a huge risk of memory leakage. We use stringbuilder to concatinate string so that no new address will be created.

Muhammad Imran Ansari · Answer

In .Net Framework Strings are immutable reference types. All .net datatypes has default size except string and user type. So String is a Reference type, because it does not have default allocation size. Immutable means, it cannot be changed after it has been created. Every change to a string will create a new string. This is why all of the String manipulation methods return a string. A Value Type holds the data within its own memory allocation and a Reference Type contains a pointer to another memory location that holds the real data. For an example, an integer (System.Int32 ) has a fixed memory size(4 bytes) of Value range -2,147,483,648 through 2,147,483,647. Hence, an integer can be stored on the Stack (i.e. fixed memory). Alternatively, a String does not have a pre-defined memory size and it can be huge(the value range may be 0 to approximately 2 billion Unicode characters), so it requires dynamic memory allocation. string yourString1 = "my string" ; //some code here string yourString2 = "my string" ; Chances are that both instances of "my string" constant will be allocated in your assembly only once. If you would like to manage strings like usual reference type, put the string inside a new StringBuilder(string s). Or use MemoryStreams.

Nitin Sontakke · Answer

And a bit of academic / technical detail. As we all know, reference types are stored on heap and value types are stored on stack.