我应该为界面中的每个按钮创建一个类吗？

Question

I have a question, i watched a lot of tutorial about MVVM but i'm still confused. I have an interface with more than one button on it, i have to implement the ICommand interface for bind the command to the View.

I did it like this:

MainSolution

Main Solution
    Model
        SomeClass.cs
    ViewModel
        Commands
            SomeCommands.cs
        SomeViewModel.cs

Ok, now in the interface i have more than one button, each one do separate things, example, one is for start a thread the other one for cancel it and a third one for another thing. Should i create a separate class, that implement ICommand interface, for each button that i have on the View?

Main Solution
    Model
        SomeClass.cs
    ViewModel
        Commands
            StartCommands.cs
            CancelCommands.cs
            OtherCommands.cs
        SomeViewModel.cs

I'm asking this because when i implement the ICommand interface i have only one "Execute" method, and only one "CanExecute" method. What is the common way to implement multiple button on a View through binding?

I searched for example online without any luck... A lot of them are so confusing, and surely not for a newbie like me.

The other thing is when i have multiple View and Multiple ViewModel, should i create multiple Commands Folder for nesting it?

Main Solution
    Model
        SomeClass.cs
    ViewModel
        FirstCommands
            StartCommands.cs
            CancelCommands.cs
            OtherCommands.cs
        SecondCommands
            StartCommands.cs
            CancelCommands.cs
            OtherCommands.cs
        FirstViewModel.cs
        SecondViewModel.cs

Answer 1

IMHO having a separate class for each command in a classic MVVM approach is an overkill. Use something like the MVVMLight's RelayCommand (and the generic one if you want to pass a parameter).

Then you can define your commands as your ViewModel members and provide Execute / CanExecute implementation as part of your ViewModel as well:

public RelayCommand MyCommand { get; }

public MyView()
{
    //[...]
    this.MyCommand = new RelayCommand(this.ExecuteMyCommand, this.CanExecuteMyCommand);
}

public void ExecuteMyCommand()
{
   //do work!
}

public bool CanExecuteMyCommand()
{
   //optional - control if command can be executed at a given time
}

And you can bind to MyCommand in XAML (assuming your View is bound to your ViewModel):

<Button Content='WORK!' Command='{Binding MyCommand}' />

Answer 2

What you want is a DelegateCommand class. You can use Prism , or just google around and steal one; here's one on StackOverflow that I haven't tested but it looks legit. If you don't need a parameter for a command, just ignore the parameter argument.

A DelegateCommand implements ICommand , and calls an Action or Action<object> that you pass to its constructor, like so (from the StackOverflow answer linked above):

public DelegateCommand AddFolderCommand { get; protected set; }
public MyViewModel(ExplorerViewModel explorer)
{           
    AddFolderCommand = new DelegateCommand(ExecuteAddFolderCommand, (x) => true);
}

public void ExecuteAddFolderCommand(object param)
{          
    MessageBox.Show("this will be executed on button click later");
}

This should have been included in WPF, but wasn't, for whatever reason.