Validation controls are provided by ASP.NET

There are six main types of validation controls:-
1.RequiredFieldValidator-
It checks whether the control have any value. It is used when you want the control should not be
empty.After apply it on control , users should compulsory to fill value in that control. For Example-In login page-

2.RangeValidator-
It checks if the value in validated control is in that specific range. Example TxtCustomerCode
should not be more than eight lengths. For Example-

3.CompareValidator-
It checks that the value in controls should match some specific value. Example Textbox TxtPie
should be equal to 3.14. For Example- For conforming password in user account page-

4.RegularExpressionValidator-
When we want the control, value should match with a specific regular expression.For Example-
Suppose you want to validate email in textbox,then you use RegularExpressionValidator with specific RegularExpression.

5.CustomValidator-
It is used to define User Defined validation.For Example-
Suppose you want to enter character between 6 to 15 in any textbox(username)-