What makes WPF application startup slow?

Question

I noticed that WPF application startup is sometimes pretty slow. Does anybody know if the the cause is the elements initialization or DLLs loading or something else?

Answer 1

The most useful advice on fixing WPF startup performance I've ever seen was given in this other question: run "ngen update" in every framework folder.

It seems that Microsoft can't keep their ngen cache up-to-date, which results in your application pretty much recompiling half the .NET framework every single startup.

Hard to believe, but seems to be true.