MVVM

CodeMonkeys.MVVM

This package contains default MVVM implementations like PropertyChanged and some "convenience implementations" to make life a little easier.

Using our ICommand implementations

The namespace of our implementations is CodeMonkeys.MVVM.Commands, so your using directive would look like this:

using CodeMonkeys.MVVM.Commands;

1. Keeping it simple: Command

public class LoginViewModel
{
    public string UserName
    {
        get => return GetValue<string>();
        set => SetValue(value);
    }

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

    public ICommand ClearUserNameCommand => new Command(() => UserName = string.Empty);
    public ICommand ClearPasswordCommand { get; }    

    public LoginViewModel()
    {
        ClearPasswordCommand = new Command(ResetPassword);
    }

    private void ResetPassword() { ... }
}

2. Defining the parameter type: Command<TParameter>

public class ItemsListViewModel
{
    public IList<Item> Items
    {
        get => return GetValue<IList<Item>>();
        set => SetValue(value);
    }

    public ICommand SelectItemCommand => new Command<Item>((item) => SelectItem(item));   

    private void SelectItem (Item selectedItem) { ... }
}

3. Want to do some asynchronous stuff? AsyncCommand

public class LoginViewModel
{
    public ICommand LoginCommand => new AsyncCommand(Login);   

    private async Task Login () { ... }
}

4. Async and defined: AsyncCommand<TParameter>

public class ItemsListViewModel
{
    public IList<Item> Items
    {
        get => return GetValue<IList<Item>>();
        set => SetValue(value);
    }

    public ICommand ShowItemDetailsCommand => new AsyncCommand<Item>((item) => ShowItemDetails(item));   

    private async Task ShowItemDetails (Item selectedItem) { ... }
}

Attributes

In the namespace CodeMonkeys.MVVM.Attributes we provide you some functionality to adapt the INotifyPropertyChanged process to your needs:

DependsOn

Target: Property
Can use multiple times: yes
Is inherited: yes

Indicates that this property's value relies on some other property (or properties).
This is the case for calculated properties like age.

In the following example, whenever DateOfBirth changes, the PropertyChanged event is also raised for Age.

public class Person :
    ModelBase
{
    public DateTime DateOfBirth
    {
        get => return GetValue<DateTime>();
        set => SetValue(value);
    }

    // we want a PropertyChanged event for Age whenever the DateOfBirth changes
    [DependsOn(nameof(DateOfBirth)]
    public int Age
    {
        get => return (DateTime.Now - DateOfBirth).Years;
    }
}

DontAffectIsDirty

Target: Property
Can use multiple times: no
Is inherited: yes

Use this attribute when you want PropertyChanged support for a property, but dont want it to affect your model's IsDirty flag.

public class Item
{
    // IsDirty should not be set to true when IsSelected changes
    [DontAffectIsDirty]
    public bool IsSelected
    {
        get => return GetValue<bool>();
        set => SetValue(value);
    }
}

SuppressNotifyPropertyChanged

Target: Class, Property
Can use multiple times: no
Is inherited: yes

This attribute prevents PropertyChanged events from being raised. You can use it on both classes and properties and can even disable the event for a whole class but exclude one property.

public class Model
{
    // we dont want to raise a PropertyChanged event when Name changes
    [SuppressNotifyPropertyChanged]
    public string Name
    {
        get => return GetValue<string>();
        set => SetValue(value);
    }
}
-----------------------------------------------------------------------------
// we dont want to raise a PropertyChanged event for any of Model's properties
[SuppressNotifyPropertyChanged]
public class Model
{
    ...
}
-----------------------------------------------------------------------------
// we dont want to raise a PropertyChanged event for any of Model's properties...
[SuppressNotifyPropertyChanged]
public class Model
{
    // ... but we want one for Name
    [SuppressNotifyPropertyChanged(false)]
    public string Name
    {
        get => return GetValue<string>();
        set => SetValue(value);
    }
}