Check if URL prototocol is handled on windows

UrlProtocol.cs

using System;
using System.IO;
using System.Security;
using Microsoft.Win32;

static class UrlProtocol
{
    public static bool IsSupported(string protocol)
    {
        if (protocol == null) throw new ArgumentNullException("protocol");
        
        RegistryKey rootKey = null;
        RegistryKey commandKey = null;
        try
        {
            rootKey = Registry.ClassesRoot.OpenSubKey(protocol);
            if (rootKey == null) return false;
            if (rootKey.GetValue("URL Protocol") == null)
            {
                return false;
            }
            commandKey = rootKey.OpenSubKey(@"shell\open\command");
            if (commandKey == null) return false;
        
            return commandKey.GetValue(null) != null;
        }
        catch (SecurityException)
        {
            return false;
        }
        catch (IOException)
        {
            return false;
        }
        catch (UnauthorizedAccessException)
        {
            return false;
        }
        finally
        {
            if (rootKey != null) rootKey.Close();
            if (commandKey != null) commandKey.Close();
        }
    }
 }
 
 /* USAGE (LINQPad) :
 
 	UrlProtocol.IsSupported("callto").Dump();
	UrlProtocol.IsSupported("tel").Dump();
	UrlProtocol.IsSupported("http").Dump();
	UrlProtocol.IsSupported(".doc").Dump();
 
 */