Get Your Feet Wet with Breeze.sharp

If you’re a .NET developer familiar with Visual Studio, here’s the quickest way to get your feet wet with Breeze.sharp. We’ll build a WPF client application from scratch that accesses IdeaBlade’s public SampleService. This service supplies TodoItem entities used by our Todo sample application, each containing a Description field along with the date created and some other flags. To keep thinks simple, we’ll only retrieve the Description fields and display them in a WPF window.

In Visual Studio, use the standard project template to create a new WPFApplication project.
In the project’s Manage Nuget Packages dialog, search online for and install the Breeze.Sharp package. Several additional dependencies will be automatically installed as well. You’ll need to accept a Microsoft license.
Add a new class named TodoItem for the model of the entities we’ll query from the server. The name “TodoItem” corresponds to the name of the entity on the server.

a. Change the namespace to Todo.Models (Again, this corresponds to the namespace used by the server)

b. Make the class public.

c. Make it inherit from Breeze.Sharp.BaseEntity

d. Add public properties for the Id (required because it’s the primary key for the entity type) and Description fields (what we’ll display):
```
public int Id {
get { return GetValue<int>(); }
set { SetValue(value); }
}
	
public string Description {
get { return GetValue<string>(); }
set { SetValue(value); }
}
```
Note that we only need to include the key field (Id) and the subset of properties we’re interested in.

In the MainWindow class (the code-behind for MainWindow.xaml):

a. Add using statements for the System.ComponentModel, Breeze.Sharp, and Todo.Models namespaces

using System.ComponentModel;
using Breeze.Sharp;
using Todo.Models;

b. Add the INotifyPropertyChanged interface to the class and let VS implement it (right click and select Implement Interface)

public partial class MainWindow : Window, INotifyPropertyChanged

c. Add an Items property that will expose the items we’ll query:

// Bindable property
public IEnumerable<TodoItem> Items {
	get { return _items; } 
	set {
		_items = value;
		if (PropertyChanged != null) { 
    		PropertyChanged(this, new PropertyChangedEventArgs("Items"));
		}
	}
}
private IEnumerable<TodoItem> _items;

Override the base BeginInit() method, adding the async keyword and invoke the base class method:

public override async void BeginInit() {
    base.BeginInit(); Within this method,

a. Set DataContext to this window to facilitate WPF binding.

DataContext = this;

b. Tell Breeze where to find our partial model of the TodoItem entity

Configuration.Instance.ProbeAssemblies(typeof(TodoItem).Assembly);

c. Create an EntityManager and configure its metatdata store to allow use of our partial model

// Create an EntityManager
var entityManager = new EntityManager("http://sampleservice.breezejs.com/api/todos/");

// Allow use of a partial model of server entities
entityManager.MetadataStore.AllowedMetadataMismatchTypes = MetadataMismatchType.AllAllowable;

d. Invoke an async method to query the TodoItems and perform rudimentary error handling:

// Query all TodoItems from the IdeaBlade-supplied public service
Items = await QueryTodosFrom(entityManager);

Create an async method to perform the query:

private async Task<IEnumerable<TodoItem>> QueryTodosFrom(EntityManager entityManager) {
    try {
        return await new EntityQuery<TodoItem>().Execute(entityManager);
    }
    catch (Exception e) {
        MessageBox.Show(e.GetType().Name + ": " + e.Message);
        return new TodoItem[0];
    }
}

In the MainWindow.xaml file add a ListView within the element to display the Description fields of the queried items:
```
<ListView ItemsSource="{Binding Items}" DisplayMemberPath="Description" />
```
Build and run the application. The list of six queried Todo items should appear in the main window.

Reference Code

Here’s the complete code for the model in TodoItem.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Todo.Models
{
    public class TodoItem : Breeze.Sharp.BaseEntity {
        public int Id {
            get { return GetValue<int>(); }
            set { SetValue(value); }
        }

        public string Description {
            get { return GetValue<string>(); }
            set { SetValue(value); }
        }
    }
}

And here’s the code behind in MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

using System.ComponentModel;
using Breeze.Sharp;
using Todo.Models;

namespace WpfApplication5
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public MainWindow() {
            InitializeComponent();
        }

        public event PropertyChangedEventHandler PropertyChanged;

        // Bindable property
        public IEnumerable<TodoItem> Items {
            get { return _items; }
            set {
                _items = value;
                if (PropertyChanged != null) {
                    PropertyChanged(this, new PropertyChangedEventArgs("Items"));
                }
            }
        }
        private IEnumerable<TodoItem> _items;

        public override async void BeginInit() {
            base.BeginInit();

            DataContext = this;

            Configuration.Instance.ProbeAssemblies(typeof(TodoItem).Assembly);

            // Create an EntityManager
            var entityManager = new EntityManager("http://sampleservice.breezejs.com/api/todos/");

            // Allow use of a partial model of server entities
            entityManager.MetadataStore.AllowedMetadataMismatchTypes = MetadataMismatchType.AllAllowable;

            // Query all TodoItems from the IdeaBlade-supplied public service
            Items = await QueryTodosFrom(entityManager);
        }

        private async Task<IEnumerable<TodoItem>> QueryTodosFrom(EntityManager entityManager) {
            try {
                return await new EntityQuery<TodoItem>().Execute(entityManager);
            }
            catch (Exception e) {
                MessageBox.Show(e.GetType().Name + ": " + e.Message);
                return new TodoItem[0];
            }
        }
    }
}