为什么` <Button Command={x:Static…}..>`有效但`</button> <Button Command={Binding…}..>`不有效？</button>

Question

I'm new to WPF, and I'm trying to implement a custom Command , what I did is that I implemented the ICommand interface and I bound that implementation to a button using two ways one with a Static Extention Marckup and one with a normal Binding, it works fine with {x:Static} , but fails with this error when using {Binding}

System.Windows.Data Error: 39 : BindingExpression path error: 'StartCommand' property not found on 'object' ''ViewModel' (HashCode=30880833)'. BindingExpression:Path=StartCommand; DataItem='ViewModel' (HashCode=30880833); target element is 'Button' (Name=''); target

here is my code

XAML

<Window x:Class="Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="75" Width="300">
    <StackPanel Orientation="Horizontal" Height="30">
        <Button Command="{Binding StartCommand}" Content="Start" Margin="5,0"/>        
        <TextBlock Text="{Binding Name}"/>
    </StackPanel>
</Window>

Code behind

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();
        DataContext = new ViewModel { Name = "Simple property" };
    }
}

class ViewModel
{
    public string Name { get; set; }
    // static to use with {x:Static}
    public ICommand StartCommand = new StartCommand();
}

class StartCommand : ICommand
{
    public bool CanExecute(object parameter)
    {
        return false;
    }

    public event System.EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameter)
    {
        MessageBox.Show("Start Executed");
    }
}

What's wrong with my code? am I messing something? thanks in advance.

Answer 1

Because

You can make x:Static references to static fields or properties

whilst field is not a valid binding source and you need to convert it into property:

public ICommand StartCommand { get; set; }

and initialize it for example in costructructor

public ViewModel()
{
   StartCommand = new StartCommand();
}