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I am trying to bind a CommandParameter to a SelectedItem property of a DataGrid. Actually, the method is called only one time at the Window invocation.

This is what I usually do with Silverlight 5 which works pretty well. 

<Button Command="{Binding DeleteProductCommand}" CommandParameter="{Binding ElementName=ProductDataGrid, Path=SelectedItem}"/>
...
<sdk:DataGrid x:Name="ProductDataGrid" AutoGenerateColumns="False" IsReadOnly="True" ItemsSource="{Binding ProductsCollection}">
...

I have read in the following post about the way commands are handled between SL and WPF. This is actually 4 years old. So I was just wondering if Microsoft released an update for this problem.

To cope with this problem I had to add a custom method called RaiseCanExecuteChanged in my command to fire the CanExecuteChanged event. Then I added a property in my ViewModel. I call the RaiseCanExecuteChanged method from the set accessor. Then I implemented the INotifyPropertyChanged interface in my ViewModel to warn the UI when the SelectedProduct property changes. 

class MainVM : INotifyPropertyChanged
{
    private Product _SelectedProduct;
    public Product SelectedProduct
    {
        get
        {
            return this._SelectedProduct;
        }
        set
        {
            this._SelectedProduct = value;
            this._PropertyChanged();
            this.DeleteProductCommand.RaiseCanExecuteChanged();
        }
    }

    private void _PropertyChanged([CallerMemberNameAttribute] string PropertyName = "")
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;

    ...
}

XAML

<Button Command="{Binding DeleteProductCommand}" CommandParameter="{Binding SelectedProduct"/>
...
<sdk:DataGrid x:Name="ProductDataGrid" AutoGenerateColumns="False" IsReadOnly="True" ItemsSource="{Binding ProductsCollection}" SelectedItem="{Binding SelectedProduct}">

I would like to know if there is a better solution than that. Actually I tried the solution from the post I mentioned earlier but I have slight lags with the UI as it refreshes all the bindings of the Window.

Any help would be much appreciated !

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Frank
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  • Is the DeleteProductCommand exposed as a property in your viewmodel? If so, the SelectedProduct is a property in the viewmodel, why do you need to pass it to the command, if the command is also in the viewmodel you should have access to SelectedProduct. – Stephen Wilson Mar 26 '15 at 16:53
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    This is pretty much how things work. It's definitely the simplest way to do it. And, no, there aren't any new advances on the ICommand front in the framework. –  Mar 26 '15 at 16:58
  • This is right. DeleteProductCommand and SelectedProduct are both part of the same ViewModel. But originally I didn't have the SelectedProduct property as I didn't need it. I added it only for this purpose. – Frank Mar 26 '15 at 21:46

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