In C++, we can use ptr = nullptr to change the pointer itself and *ptr to modify the object the pointer references. For example:
int* ptr = new int(5);
*ptr = 10; // Modifies the object
ptr = nullptr; // Changes the pointer itself
In C#, we have similar scenarios with references. For instance:
StringBuilder sb = new StringBuilder("Hello");
sb.Append(" World"); // Modifies the object
sb = null; // Sets the reference to null
My question is about the syntax and why it behaves differently. Specifically:
When I use sb.Append(), it operates on the object sb points to, not the reference itself.
When I use sb = null, it sets the reference to null, but doesn't affect the object.
Why doesn't the syntax of sb = null in C# get interpreted as setting the object to null, similar to how ptr = nullptr works in C++? Or in other words, why don't I have to dereference sb to call the Append() method? In C#, why isn't there a need to explicitly dereference the reference to perform operations on the object and how does it know when to dereference a pointer and when to manipulate it directly?
I have read up on this, but haven't found a good explanation. All that I have learned till now is that C# probably doesn't allow us to dereference explicitly but isn't that very puzzling? Like conceptually I might know that sb = null cannot set the referenced pointer to null but isn't the syntax saying otherwise or at least is unambiguous?
I'm looking for clarity on why the syntax in C# doesn't directly map to pointer manipulation in C++ and how the language ensures this distinction.
It's actually not so much different to C++ in syntax. Conceptually, reference type variables in C# and pointers in C++ do share a common base, even though there are quite a few detail differences. But since you asked about the syntax, the case is easier:
In C++ you would write:
StringBuilder* sb = new StringBuilder();
(*sb).Append(...);
sb = nullptr; // well, rather delete first, but we don't care here.
The (*sb).Append() is usually abbreviated as sb->Append(). And now we're already very close to C#, because you can just think that in C#, the -> operator is also just written as .. It's just that the compiler is "smart" enough to know whether the member-access operator has a reference type or a value type on its left side.