MVVM Pattern Implementation in Silverlight - part 1 :
In this article we would see a implementation of MVVM Pattern using Silverlight .
Checked out the following link :
http://weblogs.asp.net/dwahlin/archive/2009/12/08/getting-started-with-the-mvvm-pattern-in-silverlight-applications.aspxI just loved the Implementation by
dwahlin. The implementation is very simple and easy to code . I have modified the implementation to talk to database.
Created a new Silverlight Project named as MVVMBasic .
Created a new DataModel as shown below :
Created a new Silverlight Enabled WCF Service as shown below :
public class DataService
{
[OperationContract]
public List GetPeople()
{
ProjectsDataEntities context = new ProjectsDataEntities();
var persons = from person in context.People
select person;
return persons.ToList();
}
[OperationContract]
public OperationStatus UpdatePerson(Person p)
{
try
{
ProjectsDataEntities context = new ProjectsDataEntities();
Person currperson = (from person in context.People
where person.id == p.id
select person).First();
currperson.LastName = p.LastName;
currperson.FirstName = p.FirstName;
context.SaveChanges();
return new OperationStatus { Status = true };
}
catch (Exception ex)
{
return new OperationStatus { Status = false };
}
}
}All the remainging things I have retained from the article by
dwahlin .
Dwahlin returns the update status from the database in a nice way.
He uses a class PeopleEventBus as shown below: Basically this is a event handler to track the Completed Database Update Operation .
public static class PeopleEventBus
{
public static event EventHandler OperationCompleted;
public static void OnOperationCompleted(object sender, OperationCompletedEventArgs e)
{
if (OperationCompleted != null)
{
OperationCompleted(sender, e);
}
}
}The Custom Event Args class which has the OperationStatus as a property .
public class OperationCompletedEventArgs : EventArgs
{
public OperationStatus OperationStatus { get; set; }
}Finally the Operation status class :
public class OperationStatus
{
public bool Status { get; set; }
public string Message { get; set; }
} The below lines of code take care of catch the event and displaying the status :
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
this.ViewModel = this.Resources["ViewModel"] as PeopleViewModel;
PeopleEventBus.OperationCompleted += new EventHandler(PeopleEventBus_OperationCompleted);
}
void PeopleEventBus_OperationCompleted(object sender, OperationCompletedEventArgs e)
{
MessageBox.Show("Operation Status: " + e.OperationStatus.Status.ToString());
}In the View Model we add the below line where WCF method returns the status :
void UpdatePerson_Completed(object sender, UpdatePersonCompletedEventArgs e)
{
PeopleEventBus.OnOperationCompleted(this, new OperationCompletedEventArgs { OperationStatus = e.Result });
}Lets give this a run .
Let me modify the row and see if the update works :
Great it works.
In my next post I will add commanding to this example . Till then Happy Coding .