Designing and manipulating data set for a list with dynamic columns

I am looking for a relatively clean way to manipulate list data with regards to the following criteria. I have never worked on such a flexible application, and I want to avoid coding myself into a corner. I am looking for patterns or libraries that can help me through this. It is for a C# WPF application.

The first criterion is that the list can contain any number of (pre-defined or potentially user-defined) columns, and I want to be able to manipulate the column set cleanly (to display the list, perform operations on the list, modify the column set, etc.). The main concern here is avoiding bloating the list with unneeded data.

The second criterion is that each column can have a different format (and validation rule set), such as date, number, dropdown with set values, and so on. How can these rules be defined for each column (attribute) in an unobtrusive way?