C# catch exception being ignored thus application crushes

Question

0.00/5 (No votes)

See more:

I need to make an application in WinForm C# as my final programming project. The project is about managing Registry more nicely to make it easier for the user to edit values.
The problem is, when I read whether the UninstallString exists or not, the function for some reason doesn't look in the catch inside the try when it fails (and it fails since the app isn't 64-bit, thus the Registry value needs to be accessed differently)

public bool ValueExists(string Key, string Value)
    {
        try
        {
            try
            {
                RegistryKey rk = Registry.LocalMachine.OpenSubKey(Key);
                return rk.GetValue(Value) != null; //Error happens here when selected 64-bit application. System.NullReferenceException: 'Object reference not set to an instance of an object.'
            }
            catch (NullReferenceException ex)
            {
                RegistryKey regkey64 = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64);
                RegistryKey rk64 = regkey64.OpenSubKey(Value);
                return regkey64.OpenSubKey(Key).GetValue(Value) != null;
            }
        }
        catch
        {
            return false;
        }
    }

System.NullReferenceException: 'Object reference not set to an instance of an object.' - This is the error and I KNOW it happens cause I select a 64-bit application, but for some reason it ignores the catch.

What I have tried:

try
            {
                RegistryKey regkey64 = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64);
                RegistryKey rk64 = regkey64.OpenSubKey(Value);
                return regkey64.OpenSubKey(Key).GetValue(Value) != null;
            }
            catch (NullReferenceException ex)
            {
                RegistryKey rk = Registry.LocalMachine.OpenSubKey(Key);
                return rk.GetValue(Value) != null;
            }

If I swap the order so when I select a 64-bit Registry value it doesn't crash, but when I select a 32-bit Registry value it crashes with the same error.
rk is null under the right circumstances - which means if the selected 32-bit Registry value doesn't exists. But again, if the selected Registry value is 64-bit it'd be unreadable, thus I need to use the code in the try inside the catch (to check whether a 64-bit Registry value exists or not).

Posted 4-Nov-20 23:09pm

WillingMost7

Updated 4-Nov-20 23:30pm

Add a Solution

2 solutions

Solution 1

Why are you relying on a NullReferenceException to check the code is correct. You should test the returned value from any of the Registry calls to see if it is null before proceeding. You should never write code like:

C#

RegistryKey rk = Registry.LocalMachine.OpenSubKey(Key);
return rk.GetValue(Value) != null;

Since the returned value from OpenSubKey may be null.

Posted 4-Nov-20 23:17pm

Richard MacCutchan

Comments

WillingMost7 5-Nov-20 5:26am

If the value I'm looking for exists then it's not null

Richard MacCutchan 5-Nov-20 5:27am

Well that is pretty obvious.

WillingMost7 5-Nov-20 5:28am

Ok, so how else do you suggest to write it?

Richard MacCutchan 5-Nov-20 5:45am

I already suggested it: always check return values from system calls to see whether they are null.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Accepted Answer · 2020-11-04T23:31:00

You're potentially throwing another NullReferenceException from within your first catch block.

But you don't need either of those catch blocks:

C#

public bool ValueExists(string Key, string Value)
{
    using (RegistryKey rk = Registry.LocalMachine.OpenSubKey(Key, false))
    {
        if (rk != null) return rk.GetValue(Value) != null;
    }
    
    if (Environment.Is64BitOperatingSystem && !Environment.Is64BitProcess)
    {
        using (RegistryKey hklm = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64))
        using (RegistryKey rk = hklm.OpenSubKey(Value, false))
        {
            if (rk != null) return rk.GetValue(Value) != null;
        }
    }
    
    return false;
}