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https://github.com/klemmchr/MvvmBlazor

A lightweight Blazor Mvvm Library
https://github.com/klemmchr/MvvmBlazor

bindingsource blazor blazor-server blazor-wasm mvvm mvvm-framework viewmodel

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A lightweight Blazor Mvvm Library

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README 

        
MvvmBlazor

================

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MvvmBlazor is a small framework for building Blazor WebAssembly and Blazor Server apps. With its easy-to-use MVVM pattern you

can increase your development speed while minimising the effort required to make it work.



## Getting started



MvvmBlazor is available on [NuGet](https://www.nuget.org/packages/MvvmBlazor). You will need **.NET 6** 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.



```c#

public class Startup

{

    public void ConfigureServices(IServiceCollection services)

    {

        services.AddMvvm();

    }

}

```



## Usage



### Components



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` 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.



#### BindingSource



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` where `T` is your view model type. You can access it via

the `BindingContext` property in your component.



#### Bindings



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`.



```c#

@inherits MvvmComponentBase



Current time: @Bind(x => x.DateTime)

```



Bindings can also be done by specifying the binding source explicitly:



```c#

@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.



#### Collection Bindings



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`.



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



```c#

class MainViewModel

{

    public ObservableCollection 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



```c#

@foreach (var item in Bind(x => x.Items))

{

    @Bind(item, x => x.Name)

}

```



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.



### EventHandlers



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.



```c#

@inherits MvvmComponentBase

@inject CounterViewModel CounterViewModel



Click me

```



When using the generic base class you can directly bind them to your binding context.



```c#

@inherits MvvmComponentBase



Click me

```



### ViewModel



View models need to inherit the base class `MvvmBlazor.ViewModel.ViewModelBase`.



If you register a view model as scoped it will be tied to the lifetime of the component and disposed when the component is disposed.

This allows you to inject scoped services that should be short lived (e.g. a `DbContext`) without the need for using a factory.



Note: Some services need to be resolved from the root service provider (e.g. `NavigationManager`). To do this you can access the root service provider via the `RootServiceProvider` property.



#### Property implementation



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:



```c#

private int _currentCount;

public int CurrentCount

{

    get => _currentCount;

    set => Set(ref _currentCount, value);

}

```



As an alternative you can leverage the power of source generators to do the tedious work for you.

Just declare a private field inside of a view model and decorate if with the `Notify` attribute. The matching property will be auto generated for you.

```c#

[Notify]

private int _currentCount;

```

Note: Some third party IDEs may not recognize source generators at the current point. They could report that the property does not exist while the project builds fine.



#### Lifecycle methods



View models have access to the same lifecycle methods as a component when they are set as a binding context. They are

documented [here](https://docs.microsoft.com/en-us/aspnet/core/blazor/components?view=aspnetcore-3.0#lifecycle-methods).



#### Parameters



Parameters are automatically populated to the view model. Declare a parameter in your component



```c#

@code {

    [Parameter]

    public string Name { get; set; }

}

```



and declare the same parameter in your view model



```c#

class ViewModel: ViewModelBase

{

    [Parameter]

    public string Name { get; set; }

}

```



Cascading parameters are supported as well.

The parameter will be passed when parameters are set on the component. More information regarding the lifecycle can be

found in

the [Microsoft Documentation](https://docs.microsoft.com/en-us/aspnet/core/blazor/components/lifecycle?view=aspnetcore-6.0#lifecycle-events)

.



##### Type conversion



When binding parameters in a component Blazor restricts you to a finite list of primitive types you can use. In some

scenarios you might want to bind to a strong type and perform automatic conversions to it. A typical use case for this

would be a strongly typed identifier that you use in your application.



View model parameters support type conversion

using [`TypeConverter`](https://docs.microsoft.com/en-us/dotnet/api/system.componentmodel.typeconverter?view=net-6.0).

Your component parameters still needs to be a supported primitive type, however your view model parameter can be

strongly typed and will get auto converted. An example for this can be found in the TypedParameter sample.



#### Dispose



Since ViewModels are being injected through dependency injection in the scope of the component the

DI [takes care](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-5.0#disposal-of-services)

of disposing ViewModels.



## Advanced scenarios

Some libraries may force you to use a different base class than `MvvmComponentBase`.

To solve this issue you can create a custom mvvm component using source generators.



Create a partial class and decorate it with the `MvvmComponent` attribute.



```c#

[MvvmComponent]

public abstract partial class CustomComponentBase : UiLibraryComponentBase

{



}

```



As a reference point see [`MvvmComponentBase`](https://github.com/klemmchr/MvvmBlazor/blob/master/src/MvvmBlazor.Core/Components/MvvmComponentBase.cs) and [`MvvmComponentBase`](https://github.com/klemmchr/MvvmBlazor/blob/master/src/MvvmBlazor.Core/Components/MvvmComponentBaseT.cs).

Both are generated by a source generator as well.



## Examples



Examples for Blazor and Serverside Blazor can be

found [here](https://github.com/chris579/MvvmBlazor/tree/master/samples).



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