How to validate a list form?

Question

Hi All,
My requirement is simple, I need to validate a simple list form with some set of conditions.
So decided to deploy application pages and use the code behind to apply the conditions and map the application page to Edit/New form of the list. Can this be done and any references?
Thanks.

Answer 1

Hi,
Per my understanding, you might want to validate a list form with custom conditions.
If the validation can be achieved by using client side technology such as JavaScript, a suggestion is that you can customize the built-in NewForm/EditForm
of the list and implement your validation there.
It is also a good choice to create a custom application page in this scenario, we can write C# code for the validation and handle the form submission.
About
how to create custom application page:
https://msdn.microsoft.com/en-us/library/ee231557.aspx?f=255&MSPPError=-2147217396
https://msdn.microsoft.com/en-us/library/ee231581.aspx
For the data accessing part, you can use SharePoint Object Model:
Add, Update and Delete List Items Programmatically in SharePoint
http://www.mindfiresolutions.com/Add-Update-and-Delete-List-Items-Programmatically-in-Sharepoint-372.php 
More information about
SharePoint Object Model:
http://msdn.microsoft.com/en-us/library/ms473633.ASPX
Best regards
Patrick Liang
TechNet Community Support