Read top 1 registry value from query

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Hi I have multiple registry entries all beginning with the same prefix but I only want to get the first record so I can read the EventMessageFile Details. So far I have this which gives me a count of the records:

C#

int count = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(@"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\").GetSubKeyNames().Where(s => s.StartsWith("CardSpace")).Count();

how do I select the first record to read the details?

Posted 3-Jun-14 0:19am

pmcm

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Prasad Avunoori 3-Jun-14 6:20am

Use FirstOrDefault()

2 solutions

Solution 2

Thanks to both you guys I've ended up with this:

C#

string servicename = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(@"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\").GetSubKeyNames().Where(s => s.StartsWith("CardSpace")).FirstOrDefault();

string dotNetFourPath = "SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\" + servicename; // "AllstateCTSNGMedbillEP"; //servicename here
            using (RegistryKey registryKey = Registry.LocalMachine.OpenSubKey(dotNetFourPath))
            {
                Console.WriteLine(registryKey.GetValue("EventMessageFile")); //returns EventMessageFile - Value Data

                string sDt = registryKey.GetValue("EventMessageFile").ToString();
                //sDt.Split('\\');                
                string[] sVar = sDt.Split('\\');
                string sYourValue = sVar[4];
                Console.WriteLine(sVar[0]);
                Console.WriteLine(sVar[1]);
                Console.WriteLine(sVar[2]);
                Console.WriteLine(sVar[3]);
                Console.WriteLine(sVar[4]);
                Console.WriteLine(sVar[5]);
                Console.WriteLine(sYourValue);
            }

Posted 3-Jun-14 0:36am

pmcm

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Raul Iloc · Accepted Answer · 2014-06-03T00:27:00

Solution 1

You have to use:

C#

Microsoft.Win32.Registry.LocalMachine.OpenSubKey(@"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\").GetSubKeyNames().Where(s => s.StartsWith("CardSpace")).FirstOrDefault();

Posted 3-Jun-14 0:27am

Raul Iloc

Comments

pmcm 4-Jun-14 6:56am

I was able to get this working in a test app that I developed, but when I copied the logic to my main application:
string serviceName = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(@"SYSTEM\\CurrentControlSet\\Services\\EventLog\\Application\\").GetSubKeyNames().Where(s => s.StartsWith(editedServiceName)).FirstOrDefault();

I'm getting this error: "Object reference not set to an instance of an object." The variable editedServiceName is valid and the registry exists (I checked it manually). This application is built using v2 of .Net Framework. Can you think of any other reason why this is failing over at this point?