如何从文本框(windows窗体)c#检查数据库中是否存在主键

I have a textbox and a button in a windows form application. I want to check if the primary key (persId) exists in my sql database/dataset (made with Visual studio) when I enter a number in the textbox and press the button. I dont know how to compare the text with persId from the database.I have a textbox and a button in a windows form