why this doesn't throw an exception

it's kind a simple question but i have the doubt see the code belows

public static String something;
    static void Main(string[] args)
    {
        try
        {
            if (something == "blah")
                System.Console.Write("ok");
        }
        catch (Exception)
        {

            throw;
        }

    }

i know that doesn't throw an exception but why? because the variable with the name something it's null and when you compare you开发者_JAVA百科're trying to get a reference with null. Can someone please explain to me why? Thanks!

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Nothing is wrong here, since you're not trying to dereference something. You are getting its value, which is null. If you tried to dereference it (ie something.somemethod()) then an exception would have been thrown.

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This is IL code generated by compiler:

IL_0002:  ldsfld     string ConsoleApplication1.Program::something
IL_0007:  ldstr      "blah"
IL_000c:  call       bool [mscorlib]System.String::op_Equality(string, string)

String.op_Equality Method:

public static bool operator == (string a, string b)

a - A String or a null reference

b - A String or a null reference

op_Equality allows to pass null references and doesn't throw exception.

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The variable, something, doesn't need to be instanced for that kind of comparison. It knows how to compare itself to a null.

So it doesn't throw an exception because

null == "string"

is a valid comparison which returns false.

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You can compare null to a string - the result is that they aren't equal. In this case Something is null - you don't have to "dereference" to use it in a comparison, the null value itself works.

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since the something variable is null, then comparing it to a string value is the same as saying

if(null == "blah")...

Clearly null and "blah" are not the same, so it will return false, it won't throw an exception.

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A string is a nullable type.

So you in the given code you compare a NULL string to a string that contains the characters "blah" and you have no else statement.

Of course I would argue using == when you are trying to compare a string is wrong.

Technically "Dog played ball with the boy\n" and "Dog played ball with the boy\0" would not equate to true when using the == comparison.