# IT:AD:EF/CodeFirst/Entities #



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## CheckList ##

* [MSDN:Conventions](http://bit.ly/uka0vP)
* [MSDN:Code First Data Annotations](http://bit.ly/snjLx2)
* http://msdn.microsoft.com/en-us/library/system.data.entity.modelconfiguration.conventions(v=vs.103).aspx  
* **Important:** For Automapper to populate Navigation properties, etc. the properties must have a set. They can be protected, or private (Automapper can handle that, but they have to be there. 
    * See: [[IT/AD/NET/Data/Mapping/]]
* For Automapper, you'll have to state that you will be using whatever subject is there (rather than create a new one) by using the opt => opt.UseDestinationObject

Example:

    .ForMember(dest => dest.WorkInstruction, opt => opt.UseDestinationValue())  //opt => opt.MapFrom(s => s))
    .ForMember(dest => dest.WorkInstruction, opt => opt.MapFrom(s => s))



Requirements to enable the use of change-tracking POCO Proxies:

* Class must be public, non-abstract, non-sealed.
* Public *virtual* get/set for all persisted properties.
* Collection based Navigation properties must implement ICollection<T>

Ref: http://bit.ly/KgJPcU



## Aggregates and Entities ##


Example:


Address:

    public class Address
    {
        public virtual int Id { get; set; }
        public virtual string Street { get; set; }
        //...
    }

User:

<sxh csharp>
    public class User
    {

        public virtual int Id { get; private set; }
        //Marking *scalar* as virtual, marks it for Proxy change tracking.
        public virtual string FirstName { get; set; }

        //1-1 Relationship:
        public virtual int BillingAddressId { get; set; }
        public virtual Address BillingAddress { get; set; }
        //...
        //Marking a *Navigation Collection* as virtual, marks it for Lazy Loading 
        public virtual ICollection<Invoice> Invoices { get { return _invoices??(_invoices = new Collection<Invoice>()); } private set { _invoices = value; }}
        private ICollection<Invoice> _invoices;
    }

</sxh>

Invoice:

<sxh csharp>

    //See above requirements to enable the use of change-tracking POCO Proxies
    public class Invoice
    {

        public virtual int Id { get; private set; }
        //1-* Relationship:
        public virtual int UserId { get; set; }
        public virtual User User { get; set; }

        //*-1 Relationship:
        //Putting an Id above a Navigation property 
        // * allows setting the Item by Id
        public virtual int CategoryId { get; set; }
        public virtual Category Category { get; private set; }

        //*-1 Relationship:
        public virtual int? Category2Id { get; set; }
        public virtual Category2 Category2 { get; private set; }

        //1-0..1 Relationship:
        public virtual int ShippingAddressId { get; set; }
        public virtual Address ShippingAddress { get; set; }

        //False 1-1 Relationship (ie, a Complex Type):
        //Build Collections on demand:
        public virtual AComplexType InvoiceDiscount { get { return _invoiceDiscount ?? (_invoiceDiscount = new AComplexType()); } }
        private AComplexType _invoiceDiscount;

        //1-* Relationship:
        //Build Collections on demand:
        public virtual ICollection<LineItem> LineItems { get { return _lineItems ?? (_lineItems = new Collection<LineItem>()); } private set { _lineItems = value; } }
        private ICollection<LineItem> _lineItems;

        //An unsetable, but saveable, calculated account:
        public virtual decimal Total {get { return (1.00m -  InvoiceDiscount.Discount) * LineItems.Sum(i => i.Amount); } private set { } }

        public virtual string Summary { get; set; }
    }

</sxh>

Category:

<sxh csharp>

    //See above requirements to enable the use of change-tracking POCO Proxies
    public class Category
    {
        public virtual int Id { get; private set; }
        //Note that we can remove Convention expecting ICollection<Invoice> 
        //and it will still create Relationship, as it is defined in FluentAPI
        public virtual bool Display { get; set; }
        public virtual string Text { get; set; }
    }

</sxh>


Category2:

<sxh csharp>

    //See above requirements to enable the use of change-tracking POCO Proxies
    public class Category2
    {
        public virtual int Id { get; private set; }
        //Note that we can remove Convention expecting ICollection<Invoice> 
        //and it will still create Relationship, as it is defined in FluentAPI
        public virtual bool Display { get; set; }
        public virtual string Text { get; set; }
    }

</sxh>

ComplexType:

<sxh csharp>

    //A complex type is one that pretends to be an separate entity, but
    //is really stored in its parent table. Requirements are:
    //* No Id
    //* 1-1 relationship
    //[ComplexType]
    public class AComplexType
    {
        public decimal Discount { get; set; }
        public string Reason { get; set; }
    }

</sxh>

LineItem:


<sxh csharp>

    //See above requirements to enable the use of change-tracking POCO Proxies
    public class LineItem
    {
        public virtual int Id { get; private set; }
        public virtual int InvoiceFK { get; set; }
        //Note that we can remove Nav Reference Nav back to Invoice
        //and it will still create Relationship, as it is defined in FluentAPI
        public virtual decimal Discount { get; set; }
        public virtual int Quantity { get; set; }

        public virtual int ProductFK { get; set; }
        public /*virtual*/ Product Product { get; set; }

        //A calculated value that is saved:
        public virtual decimal Amount { get { return (1.00m - Discount) * Quantity * Product.Price; } private set { } }
        
    }

</sxh>

Product:


<sxh csharp>

    public class Product
    {
        public virtual int Id { get; private set; }
        public virtual string Description { get; set; }
        public virtual decimal Price { get; set; } 
    }

</sxh>