Entity Framework (Code First) recursive parent

Question

I am trying to describe a tree like structure where each item is a node in the tree and can (or not) have a parent.

When describing the Node entity, this works:

public class Node
{
    public int Id {get;set;}
    public string Description {get;set;}
    public int ParentId {get;set;}
}

I get a table called Nodes with the above columns and a PK on Id. If I then add a new parameter:

public virtual Node Parent {get;set;}

for quick/easy access to the parent node, the creation code adds a foreign key constraint requiring ParentId to point to a Node Id.

Since some nodes will not have a parent, attempting to add a Node with a ParentId of 0 fails.

Is there a way to do this?

You could use int? as data type for ParentId which means that the parent id is optional and null when a node doesn't have a parent. — M.E.
– M.E., Commented Apr 23, 2015 at 19:28

Technovation · Accepted Answer · 2015-04-23 19:40:31Z

2

do you have any restriction in your data model? if not just try to make parentId nullable as this:

   public int? ParentId {get;set;}

answered Apr 23, 2015 at 19:40

Technovation

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