using System.Diagnostics;

string startupPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().ManifestModule.FullyQualifiedName);//MyAutoUpdater.WinCE's startupPath(usually the same as third party application's root folder path)
string updaterFile = Path.Combine(startupPath, "MyAutoUpdater.WinCE.exe");//MyAutoUpdater.WinCE's file path
string mainExeName = "Demo";//third party application's name
string curVersion = "1.5.2.123";//third party application's current version number
string updaterUrl = "http://www.demo.com/updater.xml";//third party application's updating XML file URL
string mainExePath = Path.Combine(startupPath, "demo.exe");//third party application's main executable file path
string silent = "true";//if upgrading silent or not

ProcessStartInfo processInfo = new ProcessStartInfo();
processInfo.FileName = updaterFile;
processInfo.WorkingDirectory = startupPath;
processInfo.Arguments = string.Format("\"{0}\" \"{1}\" \"{2}\" \"{3}\" \"{4}\"", mainExeName, curVersion, updaterUrl, mainExePath, silent);

Process process = new Process();
process.StartInfo = processInfo;
process.Start();

<?xml version="1.0" encoding="UTF-8"?>
<item>
    <version>1.5.2.123</version>
    <url>http://www.demo.com/updater.zip</url>
    <changelog>http://www.demo.com/updater.txt</changelog>
    <mandatory>true</mandatory>
</item>