Custom field type - Filtering/sorting of SharePoint does not work

Question

I have create a custom field type. I can add/edit/delete without any issue.

However when I click on the column header name to filter, it shows me the error message

Cannot show the value of the filter. The field may not be filterable, or the number of items returned exceeds the list view threshold enforced by the administrator.

Answer 1

Only fields you can filter or sort are the ones you enable indexing attribute on.

You can either do it in code or by going to list setting and enable indexing on that specific column.

SPSite site = new SPSite("http://localhost");
SPWeb web = site.OpenWeb();

SPList custList = web.Lists["Customers"];
SPField custPhone = custList.Fields["Phone Number"];

custPhone.Indexed = true;

Reference