BlazorMVVM is a small framework for building Blazor and BlazorServerside apps. With its simple to use MVVM pattern you can boost up your development speed while minimizing the hazzle to just make it work.
MvvmBlazor is available on NuGet. You will need .NET 5 to use this library.
The library needs to be added to the DI container in order to use it. This is done in your Startup class.
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddMvvm();
}
}Components need to inherit the base class MvvmBlazor.Components.MvvmComponentBase if you want to inject your view model manually. You can set a binding on any view model you like to.
If you want full support use MvvmBlazor.Components.MvvmComponentBase<T> and specify your view model type as a generic argument.
Your view model will get auto injected into the component and set as a binding context.
The binding source is the default source object a binding will be made to. It is set automatically when using the base class MvvmBlazor.Components.MvvmComponentBase<T> where T is your view model type. You can access it via the BindingContext property in your component.
Bindings are achieved via the Bind method in the component. If the value of the bound property has changed the component will be told to rerender automatically. In this example we assume that the class ClockViewModel has a property called DateTime.
@inherits MvvmComponentBase<ClockViewModel>
Current time: @Bind(x => x.DateTime)Bindings can also be done by specifying the binding source explicitly:
@inherits MvvmComponentBase
@inject ClockViewModel ClockViewModel
Current time: @Bind(ClockViewModel, x => x.DateTime)Bindings also handle background updating automatically. No need to invoke the main thread.
If you want to have a collection that automatically notifies the component when it has changed you should use one that implements INotifyCollectionChanged, e.g. ObservableCollection<T>.
In List scenarios you often chain view models to achieve bindings for every list element on it's corresponding view model. Given this view models
class MainViewModel
{
public ObservableCollection<SubViewModel> Items { get; }
}
class SubViewModel
{
private string _name;
public string Name
{
get => _name;
set => Set(ref, _name, value);
}
}you can use bindings on your sub view models like this
@foreach (var item in Bind(x => x.Items))
{
<label>@Bind(item, x => x.Name)</label>
}This way the name of every list item is bound to it's corresponding entry in the view. If you change the name on any list item, it will be changed in the view too.
Event handles work just the way they work in blazor. When you use the non generic base class you can bind any injected object on them.
@inherits MvvmComponentBase
@inject CounterViewModel CounterViewModel
<button @onclick="@CounterViewModel.IncrementCount">Click me</button>When using the generic base class you can directly bind them to your binding context.
@inherits MvvmComponentBase<CounterViewModel>
<button @onclick="@BindingContext.IncrementCount">Click me</button>View models need to inherit the base class MvvmBlazor.ViewModel.ViewModelBase.
Bindable properties need to raise the PropertyChanged event on the ViewModel.
The Set-Method is performing an equality check and is raising this event if needed.
An example implementation could look like this:
private int _currentCount;
public int CurrentCount
{
get => _currentCount;
set => Set(ref _currentCount, value);
}View models have access to the same lifecycle methods as a component when they are set as a binding context. They are documented here.
Parameters are automatically populated to the view model. Declare a parameter in your component
@code {
[Parameter]
public string Name { get; set; }
}and declare the same parameter in your view model
class ViewModel: ViewModelBase
{
[Parameter]
public string Name { get; set; }
}The parameter will be passed before OnInitialized and OnInitializedAsync are invoked. Therefore, the parameters are available from any lifecycle method.
You can't access them in your constructor and you're not supposed to do that either.
Since ViewModels are being injected through depencency injection the DI takes care of disposing ViewModels.
Examples for Blazor and Serverside Blazor can be found here.
You will find several projects in there
- BlazorServersideSample
A server for the blazor serverside sample - BlazorClientsideSample.Server
The server for the blazor clientside sample - BlazorClientsideSample.Client
The client for the blazor clientside sample
These projects act as wrapper projects for the main functionality that is shared among these examples.
- BlazorSample.Components
The components and pages for the samples - BlazorSample.ViewModels
The view models for the pages - BlazorSample.Domain
Domain logic, stuff shared between components and view models
This sample tries to incorporate a ports and adapters architectural approach and shows that this library works the same for the client and the server. It also displays the advantages of the MVVM pattern which allows you to share the logic for your frontend even when the business logic differs.
As an example the weather forecast view model just references the interface of the service that is responsible to gather data. For Blazor serverside, it directly populates it, for Blazor serverside it gathers them from an api. The advantages of such patterns will especially get interesting when Blazor Native and Blazor Embedded will be available.