Validating text field
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.
Let's give it a try, and add a Required Field Validator to our page.
We will also add a Text Box to validate, as well as a button to submit the form with.
Actually, that's all we need to test the most basic part of the Required Field Validator. Validation is only performed serverside if necessary!
I'm sure that all the attributes of the controls makes sense by now, so I won't go into details about them. You should see something like this: If your browser supports Java Script, which most modern browers do, then you will notice that the page is not being posted back to the server - the validation is performed clientside! To see how it feels, you can add enableclientscript="false" to the Required Field Validator and try again.
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.
Visit Stack Exchange You can use the sharepoint's column validator.
The idea is that a human being will be able to solve a relatively easy arithmetic problem whereas a robotic program would not even recognise it as such (in a real-world implementation the sum would not only be randomly generated, but would be presented as a slightly distorted or noisy image in order to prevent an intelligent robot from being able to decipher the question).