ToolPathUtil.cs

using System;
using System.Collections.Generic;
using System.IO;
using Microsoft.Win32;

//This is stolen from MSBuild Community Tasks
static class ToolPathUtil
{
	public static bool SafeFileExists(string path, string toolName)
	{
		return SafeFileExists(Path.Combine(path, toolName));
	}

	public static bool SafeFileExists(string file)
	{
		try { return File.Exists(file); }
		catch { } // eat exception

		return false;
	}

	public static string MakeToolName(string name)
	{
		return (Environment.OSVersion.Platform == PlatformID.Unix) ?
				name : name + ".exe";
	}

	public static string FindInRegistry(string toolName)
	{
		try
		{
			RegistryKey key = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\" + toolName, false);
			if (key != null)
			{
				string possiblePath = key.GetValue(null) as string;
				if (SafeFileExists(possiblePath))
					return Path.GetDirectoryName(possiblePath);
			}
		}
		catch (System.Security.SecurityException) { }

		return null;
	}

	public static string FindInPath(string toolName)
	{
		string pathEnvironmentVariable = Environment.GetEnvironmentVariable("PATH") ?? string.Empty;
		string[] paths = pathEnvironmentVariable.Split(new[] { Path.PathSeparator }, StringSplitOptions.RemoveEmptyEntries);
		foreach (string path in paths)
		{
			if (SafeFileExists(path, toolName))
			{
				return path;
			}
		}

		return null;
	}

	public static string FindInProgramFiles(string toolName, params string[] commonLocations)
	{
		var trials = new[] { Environment.GetEnvironmentVariable("ProgramFiles(x86)"), Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles) };
		foreach (var t in trials)
		{
			if (t == null) continue;
			foreach (string location in commonLocations)
			{
				string path = Path.Combine(t, location);
				if (SafeFileExists(path, toolName))
				{
					return path;
				}
			}
		}

		return null;
	}

	public static string FindInLocalPath(string toolName, string localPath)
	{
		if (localPath == null)
			return null;

		string path = new DirectoryInfo(localPath).FullName;
		if (SafeFileExists(localPath, toolName))
		{
			return path;
		}

		return null;
	}
}