Validating text field

18-Feb-2020 03:34

In a software project of any size, the task of determining what valid data is usually undertaken long before any code is written, and is part of an initial requirements analysis phase.Even so, we can think in general terms about the kind of data validation required for a typical application, and how it might be implemented.The password fields are a good example of a situation where you can reduce the requirements for data validation by imposing such a limit.Set the Max Length property for each password field to 16, and your validation in terms of password length is then only required to check for a valid number of characters (since the maximum number cannot be exceeded in any case).Now you will see the browser posting back to the server, but the result will be the same - the validator still works!Right now, the button does nothing, besides posting back if the page is valid.

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We will also add a Text Box to validate, as well as a button to submit the form with.We will change this by adding an onclick event to it: As you will notice, we check whether or not the page is valid, before we do anything.This is very important, since this code WILL be reached if the clientside validation is not used, for some reason.We have therefore allowed the user the opportunity to enter a title that is not on the list, such as "Doctor" or "Professor", but have restricted the length of the input string to prevent abuse.

Although not explicitly stated below, you should also impose appropriate limits on the input length for the remaining fields.To demonstrate some simple validation techniques, we will create a data entry form of the type typically found on a web page.