entity-framework-6 foreign-key-relationship

Are ForeignKey and InverseProperty attributes always applied on the many side in EF6.x

I am using Entity Framework 6.0 code-first approach in my project.

I have two entities - entity1 and entity2 that have a one-to-many relationship, so that one instance of entity1 can have one or more instances of entity2 and one instance of entity2 has only a single instance of entity1.

Question: For above scenario, will ForeignKey attribute always be mentioned in the definition of entity2 class, or it could also be specified in entity1 class definition? Similarly, is there a hard and fast rule for InverseProperty attribute that it must always be specified for entity2?

UPDATE 1

It seems that ForeignKey must always be mentioned in the entity that is on the many side of a relationship i.e. dependent entity, while InverseProperty must always be specified in the entity on the one side of a relationship i.e. principal entity. But, I am not sure.

Solution

ForeignKeyAttribute

The annotation may be placed on the foreign key property and specify the associated navigation property name, or placed on a navigation property and specify the associated foreign key name.

For a one-to-many relationship, only the entity on the "many" side has a foreign key to begin with, so it could only be used on that side.

InversePropertyAttribute

Specifies the inverse of a navigation property that represents the other end of the same relationship.

A relationship has two ends, and the attribute can be placed on either end.

For a one-to-many relationship, here's an example of it placed on the "one" end:

public class Post 
{ 
    public Person CreatedBy { get; set; } 
    public Person UpdatedBy { get; set; }
}

public class Person 
{ 
    public int Id { get; set; } 
    public string Name { get; set; } 

    [InverseProperty("CreatedBy")] 
    public List<Post> PostsWritten { get; set; } 

    [InverseProperty("UpdatedBy")] 
    public List<Post> PostsUpdated { get; set; }
}

https://msdn.microsoft.com/en-us/data/jj591583.aspx#Relationships

Here's an example on the "many" side:

[Table("Department", Schema = "dbo")]  
public class DepartmentMaster  
{  
    public ICollection<Employee> PrimaryEmployees { get; set; }  
    public ICollection<Employee> SecondaryEmployees { get; set; }  
}  

[Table("Employee", Schema = "dbo")]  
public class Employee  
{  
    [InverseProperty("PrimaryEmployees")]  
    public DepartmentMaster PrimaryDepartment { get; set; }  

    [InverseProperty("SecondaryEmployees")]  
    public DepartmentMaster SecondaryDepartment { get; set; }  
}

http://www.c-sharpcorner.com/UploadFile/ff2f08/entity-framework-code-first-data-annotations/