Question

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C#: Why is adding null to a string legal?

Here is the valid C# code:

var samsung= "xyz" + null + null + null + null + "890";  // xyz890

And this is the invalid C# code:

var iphone= null.ToString(); // compiler error

Why and how is the first statement valid and second is invalid ?

Answer 1

The + operator is used to concatenate strings, and since null is an instance of the string class it can be used as an argument to the operator. "xyz" + null ends up returning the string “xyz”, so this process is just repeated until you actually add "890".

While null can be used as a string object for an argument to a method, you cannot actually call methods on it because there’s nothing to process the method call.

Think of methods as a way for an object to process an external request and things make a bit more sense. You can send a request to an object with null as an argument for what to process, but you can’t actually ask null to process something.