How to Delete a Registry Value in C#

How to delete a registry value in C#

To delete the value set in your question:

string keyName = @"Software\Microsoft\Windows\CurrentVersion\Run";
using (RegistryKey key = Registry.CurrentUser.OpenSubKey(keyName, true))
{
    if (key == null)
    {
        // Key doesn't exist. Do whatever you want to handle
        // this case
    }
    else
    {
        key.DeleteValue("MyApp");
    }
}

Look at the docs for Registry.CurrentUser, RegistryKey.OpenSubKey and RegistryKey.DeleteValue for more info.

Delete a Registry key using C#

Try this:

string str = @"Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts";
string[] strSplit = strLocal.Split('\\');
            using (RegistryKey oRegistryKey = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts", true))
            {
                RegistryKey hdr = oRegistryKey.OpenSubKey(strSplit[strSplit.Length-2], true);
                foreach (String key in hdr.GetSubKeyNames())
                    hdr.DeleteSubKey(key);
                hdr.Close();
                oRegistryKey.DeleteSubKeyTree(strSplit[strSplit.Length - 2]);
            }

Also check: Registry in .NET: DeleteSubKeyTree says the subkey does not exists, but hey, it does!

How to delete a Registry key?

Here's one approach. Note that you have to pass true to OpenSubKey in order to get Write permission.

var hklm = Microsoft.Win32.Registry.LocalMachine;
var subkey = hklm.OpenSubKey("Software\\Wow6432Node\\WindowsApplication1", true);
subkey.DeleteSubKey("Status");

How to delete a registry value in C#?

this should work

            string keyName = @"Software\Microsoft\Cryptography";
        using (RegistryKey key = Registry.LocalMachine.OpenSubKey(keyName, true))
        {
            if (key == null)
            {
                MessageBox.Show("Value Cannot Be Found");
            }
            else
            {
                key.DeleteValue("MachineGuid");
            }
         }

I dont recommend deleting it though lol

How to delete value in registry?

If you want to delete the run history, you want to delete every value of the registry key @"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU"
minus the (default) one.

(Luckily, the framework ignore the default one when you enumerate it)

On your code, instead, you are passing the entire key path to the key.DeleteValue() which is wrong.

A right approach is to first enumerate all the values of the key and then delete, here is an example:

using (RegistryKey key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU", true))
{
     string[] values = key.GetValueNames();

     foreach (var item in values)
     {
         key.DeleteValue(item);
     }
}

Reference:
https://support.microsoft.com/en-us/kb/142298

Delete all values within a registry key using C#

I agree with Ron Beyer. I think this might be what you are looking for? Edit the registry paths and HKLM/HKCU as needed.

        string keyPath64Bit = "SOFTWARE\\Wow6432Node\\Krondorian";
        RegistryKey localMachine = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64);
        RegistryKey key64Bit = localMachine.OpenSubKey(keyPath64Bit, true);

        if (key64Bit != null)
        {
            var namesArray = key64Bit.GetValueNames();
            foreach (string valueName in namesArray)
            {
                key64Bit.DeleteValue(valueName);
            }
        }

How to delete registry key by using RegistryKey object as handle

Undocumented but calling RegDeleteKey(hKey, @"") (advapi32) will delete a key by handle (works all the way back to Win95/NT4).

I don't know what the behavior on symlinks is. It most likely deletes the link (if you specifically opened the symlink) and not the target but you just have to check to be sure.

If you don't want to rely on undocumented behavior you have to call ZwDeleteKey (ntdll) as suggested by RbMm.

C# check and delete registry key problems

Your operations for adding and deleting from the registry look good just that there is an issue with your if-else condition. If you want to check and then delete a registry entry, you should do it like this:

string KeyName = @"HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run";
string valueName = "MyApp";
string codeBase = Assembly.GetExecutingAssembly().CodeBase;

if (Registry.GetValue(KeyName, valueName, null) != null)
{
     RegistryKey registryKey = Registry.CurrentUser
         .OpenSubKey("SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run", true);
     registryKey.DeleteValue(valueName);
}

Registry.GetValue(KeyName, valueName, null) is a better way to do a null check instead of doing registryKey != null because registryKey only gets the ..CurrentVersion\\Run subkey. Instead you should drill down the actual key for your app (eg. MyApp).

Hope this helps!