1. ASP.NET Validating user input Validating user input on the client and/or server side ASP.NET Validating User Input

2. Validation • Goals • Check validity of data from the end user • How • Check user input on the client side or on the server side • Examples • Is the name TextBox empty? • Does the email TextBox contain a structurally valid email address? ASP.NET Validating User Input

3. Client-side validation Done in the browser Uses JavaScript Users can disable JavaScript! Different browsers → different JavaScript versions Does not require HTTP request + response Server-side validation Done on the server Uses C# Requires HTTP request + response Client-side vs. server-side validation ASP.NET Validating User Input

4. Client-side and server-side validation • Best practice • Client-side validation and server-side validation • Client-side saves time • No HTTP request/response • Server-side • Provides security • JavaScript not disable ASP.NET Validating User Input

5. ASP.NET Validation server controls • ASP.NET performs browser detection • Client supports JavaScript • Use client-side validation + server-side validation • Client does not support JavaScript • Use server-side validation ASP.NET Validating User Input

6. The standard validation controls • RequiredFieldValidator • Input field cannot be empty • CompareValidator • Compare between user inputs using =, >, etc. • RangeValidator • Minimum < input < maximum • RegularExpressionValidator • Check the entry matches a pattern defined by the regular expression • CustomValidator • Make your own validator • DynamicValidator • Advanced: Exceptions thrown from the model • ValidationSummary • Displays all error messages from validators in one spot • Third-party controls • Not made by Microsoft or by you • Examples: www.peterblum.com/DES ASP.NET Validating User Input

7. Some properties common to all validation controls • ControlToValidate • The control to be validated • ErrorMessage • The message used in the ValidationSummary • Text • The error message used in the validation control • CssClass • Style appearance of the messages • Example: aspnet/validation/Validation ASP.NET Validating User Input

8. Making validation happen – or not • Validation happens because of an event • Example: button click event • Can be turned of (for some buttons in a form) • <asp:Button ID=“Button1” runat=“server” Text=“Submit” CausesValidation=“false” > • Client-side validation can be turned off • Only server-side validation in effect • <asp:RequiredFieldValidator … EnableClientScript=“false”> ASP.NET Validating User Input

9. References • Bill Evjen et al. Professional ASP.NET 4 in C# and VB, Wrox 2010 • Chapter 4, Validation Server Controls, page 157-185 • W3schools.com Validation Server Controls • http://w3schools.com/aspnet/aspnet_refvalidationcontrols.asp ASP.NET Validating User Input