首先点击按钮很慢

I've created a simple application with wpf, and noticed a strange behavior: the Application has two buttons, with unrelated and very simple behaviors. Whenever I launch it, the first click of any of the buttons takes two to three seconds to complete. Only the first click is slow. Subsequent clicks are almost immediate, as expected for their simple behaviour. I've searched google and SO, but nobody seems to be experiencing the same problem.I've created a simple application with wpf, and