单击绑定到功能的UWP MVVM

Question

This is probably the easiest thing in the world to do but I'm struggling a bit.

I have this in XAML:

<Button Name="browseButton" Content="Browse" Grid.Column="1" />

I've got everything binding correctly from the view to the viewmodel, like radio buttons and input text boxes etc... but what I want is to bind this button to a function, such that when the user clicks it some operation occurs.

But I'm really having a hard time figuring out how to bind clicking this button to a function in the viewmodel. I've played a bit with ICommand and didn't get very far, and I don't want to do the hack-ish thing of just sticking it in the code behind.

I'm using MVVMLight (Galasoft) if that helps.

Any guidance appreciated.

Edit

Following the example from https://msdn.microsoft.com/en-us/magazine/dn237302.aspx I have, but where does canExecuteMyCommand come into it? And how do I bind it in the XAML?

    public RelayCommand BrowseCommand
    {
        get;
        private set;
    }

    public LoadFilesViewModel()
    {
        BrowseCommand = new RelayCommand(executeBrowse, () => _canExecuteMyCommand);
    }

    private void executeBrowse()
    {
        // Do something 
    }

Solution

<Button Name="browseButton" Content="Browse" Grid.Column="1" Command="{Binding BrowseCommand}" />

And

    public RelayCommand BrowseCommand
    {
        get;
        private set;
    }

    public LoadFilesViewModel()
    {
        BrowseCommand = new RelayCommand(executeBrowse, () => true);
    }

    private void executeBrowse()
    {
        // Do something 
    }

Answer 1

If you look at the code you provided, the RelayCommand constructor comes with 2 parameters.

public RelayCommand BrowseCommand
{
    get;
    private set;
}

public LoadFilesViewModel()
{
    BrowseCommand = new RelayCommand(executeBrowse, () => _canExecuteMyCommand);
}

private void executeBrowse()
{
    // Do something 
}

Checking the source code (that's the learning a code base and open-source makes this possible) or Visual Studio IntelliSense, you'll see this signature:

public RelayCommand(Action execute, Func<bool> canExecute)

So the first parameter is an action to be executed, and the second parameter is a check if it can execute. You've correctly identified the executeBrowse as a method to "do something". The _canExecuteMyCommand parameter is a class variable of the type bool that can be either true or false (set somewhere else).

In your own solution (posted in question), you replaced this by true (hardcoded). Note that you can also drop the second parameter in this case:

public LoadFilesViewModel()
{
    BrowseCommand = new RelayCommand(executeBrowse); // will always execute
}

Bonus

Note that instead of using a local variable, you can also use a method to defined whether the method can execute (or write the check logic inline with the delegate syntax).

public LoadFilesViewModel()
{
    BrowseCommand = new RelayCommand(ExecuteBrowse, CanExecuteBrowse);
}

private void ExecuteBrowse()
{
    // Do something 
}

private bool CanExecuteBrowse()
{
    // Check if we are allowed to browser
    return true; // or false :)
}