Validating file extension with regularexpressionvalidator
Place four controls from the Web forms section of the Toolbox onto the form. If Is Valid returns a value of true then all of the validation checks were successful.
Drag one Text Box control and give it an ID of First Name Text Box, two Button controls (Submit Button and Cancel Button), and one Required Field Validator (First Name Required Field Validator). The following screen shows the form in action, and the user has pressed the Submit button without entering any text into the textbox. The Required Field Validator fails when the value in the associated control matches the value of the Initial Value property of the Required Field Validator.
The regexp can either be supplied when the QRegular Expression Validator is constructed, or at a later time.
If the regexp partially matches against the string, the result is considered Intermediate.
As we will see later in the code-behind file, the Cancel Button will clear all of the fields on the form, and we do not want to validate any of the fields when the user presses this button. If any one of the validation controls on a form fails, the script cancels the postback operation and displays error messages on the form.
Constructs a validator with a parent object that accepts all strings that match the regular expression re. could be a valid match if additional valid characters are added), and Invalid if input is not matched.
In case the input is not matched, the pos parameter is set to the length of the input parameter; otherwise, it is not modified. Documentation contributions included herein are the copyrights of their respective owners.
Malicious users might circumvent client side validations in an effort to break-in or damage your servers.
Simply put, never trust the data in an incoming request, and always validate on the server.