Type of validation  Control to use Description
Required entry RequiredFieldValidator Ensures that the user does not skip an entry.
Comparison to a value CompareValidator Compares a user's entry against a constant value, against the value of another control (using a comparison operator such as less than, equal, or greater than), or for a specific data type
Range checking RangeValidator Checks that a user's entry is between specified lower and upper boundaries
Pattern matching RegularExpressionValidator Checks that the entry matches a pattern defined by a regular expression. This type of validation enables you to check for predictable sequences of characters, such as those in e-mail addresses, telephone numbers, postal codes, and so on
User-defined CustomValidator Checks the user's entry using validation logic that you write yourself. This type of validation enables you to check for values derived at run time.