Value Objects and Identity

1.cs

public class PlanningTool
{
    internal int Id { get; private set; }

    // Rest of class
    public ICollection<PlanningToolTab> Tabs { get; private set; }
}

public class PlanningToolTab
{
    internal int Id { get; private set; }

    public int PlanningToolId { get; private set; }
    public int PlanningToolGroupId { get; private set; }

    // Rest of class
    public ICollection<PlanningToolGroup> Groups { get; private set; }
}

public class PlanningToolGroup
{
    internal int Id { get; private set; }
    // Rest of class
}

2.cs

public class PlanningTool
{
    internal int Id { get; private set; }

    // Rest of class
    public ICollection<PlanningToolTab> Tabs { get; private set; }
}

public class PlanningToolTab
{
    public int PlanningToolId { get; private set; }         // Part of the primary key
    public int PlanningToolGroupId { get; private set; }    // Part of the primary key

    // Rest of class
    public ICollection<PlanningToolGroup> Groups { get; private set; }
}

public class PlanningToolGroup
{
    internal int Id { get; private set; }
    // Rest of class
}

3.cs

public class PlanningTool
{
    internal PlanningToolId Id { get; private set; }

    // Rest of class
    public ICollection<PlanningToolTab> Tabs { get; private set; }
}

public class PlanningToolTab
{
    public PlanningToolTabId Id { get; private set; }

    // Rest of class
    public ICollection<PlanningToolGroup> Groups { get; private set; }
}

public class PlanningToolGroup
{
    internal PlanningToolGroupId Id { get; private set; }
    // Rest of class
}

public class PlanningToolTabId : ValueObject
{
    public PlanningToolId PlanningToolId { get; }
    public PlanningToolGroupId PlanningToolGroupId { get; }
    // Equality members
}

public class PlanningToolId : ValueObject
{
    public int Value { get; }
    // Equality members
}

public class PlanningToolGroupId : ValueObject
{
    public int Value { get; }
    // Equality members
}

4.cs

public int PlanningToolId { get; private set; }

5.cs

public PlanningTool PlanningTool { get; private set; }

6.cs

// before
public int PlanningToolId { get; private set; }
public int PlanningToolGroupId { get; private set; }
// after
public PlanningTool PlanningTool { get; private set; }
public PlanningToolGroup PlanningToolGroup { get; private set; }

7.cs

customer.Id = order.Id;