获取.net框架的安装目录

        方法一：
        string frameworkInstallDir = System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory();

        方法二：
        public static string GetFrameworkDirectory()
        {
            // This is the location of the .Net Framework Registry Key
            string framworkRegPath = @"Software\Microsoft\.NetFramework";
            // Get a non-writable key from the registry
            RegistryKey netFramework = Registry.LocalMachine.OpenSubKey(framworkRegPath, false);
            // Retrieve the install root path for the framework
            string installRoot = netFramework.GetValue("InstallRoot").ToString();
            // Retrieve the version of the framework executing this program
            string version = string.Format(@"v{0}.{1}.{2}\",
            Environment.Version.Major,
            Environment.Version.Minor,
            Environment.Version.Build);
            // Return the path of the framework
            string path = System.IO.Path.Combine(installRoot, version);
            if (path.EndsWith("\\"))
            {
                return path;
            }
            else
            {
                return path + "\\";
            }
        }