Reading Registry Values

[ormonds]

I have some registry values: [HKEY_CLASSES_ROOT\WinZip\Shell\Unzip_Model]@="Unzip Model" [HKEY_CLASSES_ROOT\WinZip\Shell\Unzip_Model\command]@="\"D:\\TeklaZipping\\TeklaZipping.exe\" \"%1\" " I am trying to read the value prior to correcting it if wrong:

     RegistryKey UnZipping = Registry.ClassesRoot.OpenSubKey(@"WinZip\\Shell\\Unzip\_Model");
        if (UnZipping != null)
        {
            whattodo = UnZipping.GetValue("command").ToString();
            UnZipping.Close();
        }

the line

            whattodo = UnZipping.GetValue("command").ToString();

always gives an error System.NullReferenceException. "Object reference not set to an instance of an object." I've tried with "(Default)" instead of "command" and various other possibilities but get the same error. Clearly there is something here I don;t understand, can anyone help?

[Super Lloyd]

[This](https://stackoverflow.com/questions/974038/reading-64bit-registry-from-a-32bit-application) might be relevant? Basically there are 2 registry databases. a 64 bit and 32 bit one. Kind of messed up.... But workable! ;)

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[OriginalGriff]

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself. Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable. It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night. We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket! Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't. But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values. But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out! But even then, I'd strongly advise against using the registry unless you really have to: access to it is restricted and becoming more so with each version of Windows. (Mostly because it was abused a lot when it was first released, leading to some truly horrendous file sizes and damage.) If possible, store your info somewhere else: a config file or similar is a good idea.

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay..

[Luc Pattyn]

Google knows: How I can read Default value from registry?[^] :)

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