Testing a null reference always returns false ... even when null

Question

If I compile the following code snippet with Visual C # 2010, I ALWAYS get false:

object o = null;
Console.WriteLine("Is null: " + o == null); // returns false

Does anyone know why ???

Answer 1

Why is it easy; think about what you wrote, as a matter of fact:

object o = null;
Console.WriteLine(("Is null: " + o) == null); // returns false

Testing "Is null: " + oagainst null, which always will be false. This is due to the operator precedence rules where +preceded ==.

You must explicitly apply parens to make sure that it works the way you want:

Console.WriteLine("Is null: " + (o == null)); // returns true

As noted in the comments of Jim Rhodes :

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Answer 2

.

Try

Console.WriteLine("Is null: " + (o == null));

o "Is null: ", , . , , . ,

Console.WriteLine(false.ToString());

"False", .

Answer 3

: , . , , . :

Console.WriteLine("is null: {0}", obj == null);

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