I used the solution from Russell Gantman and rewritten it as an extension method you can use like this:
var process = Process.GetProcessesByName("explorer").First();
string path = process.GetMainModuleFileName();
// C:\Windows\explorer.exe
With this implementation:
internal static class Extensions {
[DllImport("Kernel32.dll")]
private static extern bool QueryFullProcessImageName([In] IntPtr hProcess, [In] uint dwFlags, [Out] StringBuilder lpExeName, [In, Out] ref uint lpdwSize);
public static string GetMainModuleFileName(this Process process, int buffer = 1024) {
var fileNameBuilder = new StringBuilder(buffer);
uint bufferLength = (uint)fileNameBuilder.Capacity + 1;
return QueryFullProcessImageName(process.Handle, 0, fileNameBuilder, ref bufferLength) ?
fileNameBuilder.ToString() :
null;
}
}