Here I have attached the code for parameterrized query by running this application you will understand how to use the parameterized query in C#.net Windows application.
For this application i used the northwind database so if you dont have northwind database then download it from google and change the connection string in the above attached file code.
Hope this code will help you to clear your concept about sql parameterized query.
If you have any difficulty in above code please post it as a comment below.