How SubmitChanges works in .NET RIA Servies

Now I’m back from my 4 week long vacation. I have spend a lot of time with my new apartment, took about 2 month to get most of it ready, I still have a lot of things to do, but all the painting and stuff are done :) I got a question on my e-mail regarding .NET RIA Services and the Business Application project’s UserRegistartionService. It was about the AddUser method in the Service and when and where it’s called. I thought it would be great to write a post about it.

Something that is good to have in mind is that the .NET RIA Services is all about code generation. The Business layer we are creating by following the .NET RIA Service business layer pattern and guide lines, will be used to generate proxy classes on the client-side to help us communicate to the server in a easy way. The proxy class on the client-side will use “Unit of Work” and Track changing etc. To use those features in a proper way, we have to use a specific “pattern” when we write our Business logic layer.

Note: This post is based on the July Preview of the .NET RIA Services, and I also assume you have some basic knowledge about the .Net RIA Services.

I will start with a custom DomainSerivce and how it works. Here is an example of a custom DomainService:

[EnableClientAccess()]
public class MyDomainService : DomainService
{
    private List<Customer> _customers = new List<Customer>()
                                        {
                                           new Customer() { ID = 1, Name = "John Doe" },
                                           new Customer() { ID = 2, Name = "Jane Doe" }
                                        };

    public IEnumerable<Customer> GetCustomers()
    {
        return _customers;
    }

       
    public void AddCustomer(Customer customer)
    {
        _customers.Add(customer);
    }


    public void DeleteCustomer(Customer customer)
    {
        _customers.Remove( _customers.Find(c => c.ID == customer.ID));
    }


    public void UpdateCustomer(Customer customer)
    {
        var customerToUpdate = _customers.Find(c => c.ID == customer.ID);
        customerToUpdate = customer;
    }

}


public class Customer
{
    [Key]
    public int ID { get; set; }

    public string Name { get; set; }
}

The code has a MyDomainService class and a Customer entity with two properties, ID and Name. The MyDomainService has four methods, GetCustomers, AddCustomer, DeleteCustomer and UpdateCustomer. When we build the code, the .NET RIA Services will generate our proxy classes (DomainContext) to help use communicate to the DomainService on the server-side. The generated proxy class will be add to our client project.

Here is the generated proxy classes (I have removed some code to make it smaller):

public sealed partial class Customer : Entity
{
       
    private int _id;
       
    private string _name;
       
    public Customer()
    {
       ...
    }
       
    [DataMember()]
    [Key()]
    public int ID
    {
        get
        {
            return this._id;
        }
        set
        {
            ...
            this._id = value;
            ...
        }
     }
       
     [DataMember()]
     public string Name
     {
        get
        {
           return this._name;
        }
        set
        {
            ...
            this._name = value;
            ...
        }
    }
      
    public override object GetIdentity()
    {
       return this._id;
    }
}
   
public sealed partial class MyDomainContext : DomainContext
{
    ...

    public EntityList<Customer> Customers
    {
       get
       {
          return base.Entities.GetEntityList<Customer>();
       }
    }
       
    public EntityQuery<Customer> GetCustomersQuery()
    {
       return base.CreateQuery<Customer>("GetCustomers", null, false, true);
    }

    ...      
 }

public partial class MainPage : UserControl
{
    MyDomainContext _myDomainContext = new MyDomainContext();

    
    public MainPage()
    {
        var loadOperation = _myDomainContext.Load<Customer>(_myDomainContext.GetCustomersQuery());
        loadOperation.Completed += new EventHandler(loadOperation_Completed);

    }


    void loadOperation_Completed(object sender, EventArgs e)
    {
        var lastCustomer = _myDomainContext.Customers.Last();

 

 
        lastCustomer.Name = "Last Doe";


        _myDomainContext.Customers.Add(new Customer() { ID = 3, Name = "Jones Doe" });


        _myDomainContext.Customers.Remove(_myDomainContext.Customers.First());

        _myDomainContext.SubmitChanges();
    }

In the constructor of the MainPage, the Load method of the MyDomainContext class is used. Because our generated DomainContext proxy inherits from the DomainContext base class, we have access to some methods, for example the Load and SubmitChanges method. The Load method will make an async call to the MyDomainSerivice’s GetCustomers method. When the DomainContext gets the results from the server, the loadOperation_Completed event will be “executed”. By using the MyDomainContext’s Customers property (generated by .Net RIA Services) we will have access to all the Customers that are loaded. The Customers property returns a EntitList. A DomainContext has an Entity Container, where all entities are stored. A Entity Container managed a set of EntityLists and have the responsibility to handle the changing tracking and identity management on the client.

In the code above you can see that the Name of the last customer is set to “Last Doe”. When we update an Entity, an Update operation is added to the DomainContext’s “Unit of Work”, handled by the Entity Container. No updates will take place until we tell the Entity Container to process all of the changes. The code above will also call the Add and Remove method of the Customers property. When doing so, an Add and Remove operation is added to the list of work that should be processed when we call the SubmitChanges. When the SubmitChanges is called the changes are all sent to the service all together.

Note: When we call the Add and Remove method etc, no calls to the server will take place. It will only take place when we call the SubmitChanges.

So when the SubmitChanges is called, the DomainCotnext Unit of Work will be handled. We have Updated a Entity, added an Entity and also Removed and Entity. So the SubmitChanges will now do an async. call to the DomainService, and call the methods that will handle the operations, in this case the MyDomainService’s AddCustomer, RemoveCustomer and UpdateCustomer method will be executed on the server-side.

There is a naming convention which can be used for the CRUD methods, here is a list form the .NET RIA Services documentation:

Insert

    “Insert”, “Add”, “Create” prefixes
    Method signature : void InsertX(T entity), where T is an entity Type

Update

    “Update”, “Change”, “Modify” prefixes
    Method signature : void UpdateX(T current), where T is an entity Type

Delete

    “Delete”, “Remove” prefixes
   Method signature : void DeleteX(T entity), where T is an entity Type

Query

    Method signature returning a singleton, IEnumerable<T> , IQueryable<T> where T is an entity Type, and taking zero or more parameters

Resolve

   “Resolve” prefix
   Method signature : bool ResolveX(T curr, T original, T store, bool isDelete) where T is an entity type

We can also use attributes (InsertAttribute/UpdateAttribute/DeleteAttribute/QueryAttribute/ResolveAttribute) if we don’t want to use the “reserved” words:

[Delete]
public void DestoryCustomer(Customer customer)
{
   _customers.Remove( _customers.Find(c => c.ID == customer.ID));
}

Now when you know why some methods added to a Service isn’t available on the Client-side, we can go on with the Business Application project template’s UserRegistartionService

If we take a look at the Business Application project template’s UserRegistartionService. We have the following methods:

[EnableClientAccess]
public class UserRegistrationService : DomainService
{
    public void AddUser(UserInformation user)
    {
       MembershipCreateStatus createStatus;

       Membership.CreateUser(user.UserName, user.Password, user.Email, user.Question, user.Answer, true, null, out createStatus);
       if (createStatus != MembershipCreateStatus.Success)
       {
          throw new DomainServiceException(ErrorCodeToString(createStatus));
       }
   }

   public IEnumerable<UserInformation> GetUsers()
   {
      return null;
   }
}

private UserInformation _userInformation = new UserInformation();
private UserRegistrationContext _registration = new UserRegistrationContext();

public LoginWindow()
{
   ...

   this._registration.UserInformations.Add(this._userInformation);
   this.registerForm.CurrentItem = this._userInformation;
}

As you can see, a new instance of the UserInformation entity (_userInformation) is added to the UserRegistartionContext’s UserInformations EntityList. At this case an Add operation is added to the UserRegistartionContext’s “Unit of Work”. The _userInformation is then bounded to a DataForm, which uses a two-way binding. So every changed done to the DataForm, will be done to the _userInformation object. When the Register button of the LoginWindow.xamls is called, the UserRegistrationService’s SubmitChanges method will be called, which will make sure the AddUser method of the UserRegistartionService will be executed and the _userInformation object will be passed as an argument to the AddUser method.

private void RegisterButton_Click(object sender, RoutedEventArgs e)
{
   ...

   _regOp = _registration.SubmitChanges();

   ...
}