How to update foreign key back to NULL?

Question

How do i update a foreign key column back to null?

On insert or update i use this:

getCategory = _db.Categories.Find(id);
Events.Categories = getCategory; //add foreign key

But if the category is 0 (not selected) i want to update the relationship Category_ID back to null.

Try to do it like that:

Events.Categories = null; //add foreign key

But it doesn't seems to work

Please advise
Thanks

nave · Answer

Thanks for the replay but when i insert the item with a 0 in the categoryId i get a NULL on the Category_ID DB column which is the foreign key. So is there a way to delete the relationship? Please advise Thanks

Sandeep Singh Shekhawat · Answer

A table foreign key same as primary key for another table so in sql server the primary key field can not take a null value. So we can't insert null value in foreign key field as well. Thanks Sandeep