需要帮助才能进行简单的文本框验证

i am new in wpf and i try so many tutorial for make a easy validation using ValidationRule but nothing help me, i am so confused! my problem is to implement all to my own project i have a main window when clicking on button showen a dialog that ask for enter a number and i need to make validations on this numberi am new in wpf and i try so many tutorial for