UI Improve:

Add Combo Box to select Game Level
Add a Button to Gen and Begin a Game
Add a Label to show how much time elapsed
Change the way to present the peers of selected square
Fix Bugs now square will turns to red to indicate a wrong filling properly
add a Helper Class and move some methods(like solver) into it
modify the generate and solve methods, now it can generate or solve a suduko within 1 seconds

but it's a problem that i can not explain when decide where to start clearing the "triedHistory" , details can be saw at method SudokuHelper.Solve