String reference check return true in my unit Test

Question

Below is my test case. Both string are different object yet the my test case pass.

I am expecting them to fail. Because they are different objects.

 string string1 = "Hello World";
    string string4 = "Hello World";
    Assert.AreSame(string1, string4);//Will return true
    Assert.IsTrue(object.ReferenceEquals(string1,string4));

Duplicate/Similar: https://stackoverflow.com/questions/9112610/referenceequals-working-wrong-with-strings -tl;dr compile time constants — Jaya, Jul 13 '17 at 05:15
Possible duplicate of [How does string works in c#?](https://stackoverflow.com/questions/38794835/how-does-string-works-in-c) — Samvel Petrosov, Jul 13 '17 at 05:15
Strings are saved in Table by CLR and if it is going to save string that already exists it will just return the link to the existing string. — Samvel Petrosov, Jul 13 '17 at 05:17
Possible duplicate of [ReferenceEquals working wrong with strings](https://stackoverflow.com/questions/9112610/referenceequals-working-wrong-with-strings) — Petr Abdulin, Jul 13 '17 at 05:27

Fabio · Accepted Answer · 2017-07-13T05:21:57.817

Compiler will create one "object" for equal hardcoded strings.

But if you create strings dynamically

var string1 = "Hello World";
var name = "World";
var string2 = "Hello " + name;
Assert.AreSame(string1, string2); //Will return false
Assert.IsTrue(object.ReferenceEquals(string1,string2)); // Fail
Assert.AreEqual(string1, string2); // Pass

String.Intern Method (String)

The common language runtime conserves string storage by maintaining a table, called the intern pool, that contains a single reference to each unique literal string declared or created programmatically in your program. Consequently, an instance of a literal string with a particular value only exists once in the system.

Fabian Bigler · Answer 2 · 2017-07-13T17:03:15.463

When comparing strings. If objA and objB are strings, the ReferenceEquals method returns true if the string is interned. It does not perform a test for value equality.

In the following example, s1 and s2 are equal because they are two instances of a single interned string. However, s3 and s4 are not equal, because although they are have identical string values, that string is not interned.

String s1 = "String1";
String s2 = "String1";
//string is interned

String suffix = "A";
String s3 = "String" + suffix;
String s4 = "String" + suffix;  
//string is not interned

String reference check return true in my unit Test

2 Answers2