.Net和SQL Server中的自定义字段

We have a requirement on our project for custom fields. We have some standard fields on the table and each customer wants to be able to add their own custom fields. At the moment I am not interested in how this will work in the UI, but I want to know what the options are for the back end storage and retrieval of the data. The last time I did something like this was about 10 years ago in VB6 so I would be interested to know what the options are for this problem in today's .Net world.We have a requirement on our project for custom