Or a more type safe way:
[ForeignKey(typeof(Division), AllowCascadeDeletes=true, NullReferenceValue="{00000000-0000-0000-0000-000000000000}")]
[ForeignKey(typeof(Division), AllowCascadeDeletes=true, NullReferenceValue="{00000000-0000-0000-0000-000000000000}")]