In C#, string is a reference type but why it's not changing after manipulating it in another method [duplicate]

Answer 1

That's because of way how CLR passes the params to method.

Put simply:

string sample = "Initial value";  

Here sample variable refers to "Initial value" string instance stored in heap.

public static void Test(string testString) 
{ 
    testString = "Modified Value"; 
}

In the method you modify testString variable(copy of sample variable) making it references to "Modified Value" string in a heap, leaving original sample variable no affected.