Wizard validation VM

[enrico]

Hi, I'm a new developer in WPF.

I'm looking a way to validate a page of Wizard control when the "next" button is clicked. 
Basically I have a wizard where the first step check a connection with a SQL Database. This check is made from ViewModel. I need that when the Next is pressed the ViewModel do the check and if return "true" the wizard go to next step.

How I can do this?

I know how to call a command of ViewModel from Wizard but how I can tell "go ahead"?

Thanks.

[Martin Ivanov]

Hello Enrico,

You can achieve your requirement with a custom command provider. If you override the MoveCurrentToNext() method, you can implement a custom validation and if the data is invalid avoid returning the base implementation of the method in order to prevent the navigation. Here is an example in code:

public class CustomCommandProvider : WizardCommandProvider
{
	public CustomCommandProvider() : base(null)
	{
	}

	public CustomCommandProvider(RadWizard wizard) : base(wizard)
	{
	}

	protected override void MoveCurrentToNext()
	{
		if (the result from the database is valid)
		{
			base.MoveCurrentToNext();
		}
		else
		{
			// do nothing
		}
	}
}

<telerik:RadWizard>
	<telerik:RadWizard.CommandProvider>
		<local:CustomCommandProvider />
	</telerik:RadWizard.CommandProvider>
</telerik:RadWizard>

Can you please try this and let me know if it helps?

Regards,
Martin Ivanov
Progress Telerik

[enrico]

Hi Martin,
thanks for your reply.
I had tried to use CustomCommandProvider unsuccessful. The class is in the same namespace of ViewModel, but how I can access to the property of ViewModel?
I have this situation: first page of Wizard has a list of database Cconnection and the user have to select one. On next button I have to check that the selected connection is available.
This is my ViewModel, but in MoveCurrentToNext method how I can access to ViewModel property?

namespace Dinamo.ViewModels
{
    public class StartUpWizardWindowViewModel : BindableBase
    {
        public string Title => ProductInfos.ProductName;

        private ConnectionItem _connectionSelected;
        public ObservableCollection<ConnectionItem> ListDBConnections { get; set; }
        public ConnectionItem DBConnectionSelected
        {
            get => _connectionSelected;
            set
            {
                _connectionSelected = value;
                OnPropertyChanged(new PropertyChangedEventArgs("IsDBConnectionSelected"));
            }
        }
        public bool IsDBConnectionSelected
        {
            get
            {
                return _connectionSelected != null;
            }
        }

        public StartUpWizardWindowViewModel()
        {
            ListDBConnections = new ObservableCollection<ConnectionItem>(DBProfilesManager.Instance.GetConnectionList());
        }

    }

   public class CustomCommandProvider : WizardCommandProvider
        {
            public CustomCommandProvider() : base(null)
            {
            }

            public CustomCommandProvider(RadWizard wizard) : base(wizard)
            {
            }

            protected override void MoveCurrentToNext()
            {
                //How I can access to DBConnectionSelected?
                if (DBProfilesManager.Instance.TestConnection(DBConnectionSelected.ProfiloDB))
                {
                    base.MoveCurrentToNext();
                }

                else
                {
                    // do nothing
                }
            }
        }

}

[Martin Ivanov]

Hello enrico,

On way to do this is to expose an additional property on the CustomCommandProvider class that holds a reference to the view model. For example:

public class CustomCommandProvider : WizardCommandProvider
{
	public ConnectionItem DBConnectionSelected
	{
		get { return (ConnectionItem )GetValue(DBConnectionSelectedProperty); }
		set { SetValue(DBConnectionSelectedProperty, value); }
	}

	public static readonly DependencyProperty DBConnectionSelectedProperty =
		DependencyProperty.Register(
			"DBConnectionSelected", 
			typeof(ConnectionItem), 
			typeof(CustomCommandProvider), 
			new PropertyMetadata(null));

	public CustomCommandProvider() : base(null)
	{
	}

	public CustomCommandProvider(RadWizard wizard) : base(wizard)
	{
	}

	protected override void MoveCurrentToNext()
	{
		if (DBProfilesManager.Instance.TestConnection(DBConnectionSelected.ProfiloDB))
		{
			base.MoveCurrentToNext();
		}

		else
		{
			// do nothing
		}
	}
}

Then bind it to the DBConnectionSelected property from the view model.

<telerik:RadWizard.CommandProvider>
	<local:CustomCommandProvider DBConnectionSelected="{Binding DBConnectionSelected}" />
</telerik:RadWizard.CommandProvider>

Regards,
Martin Ivanov
Progress Telerik

[enrico]

Thank you Martin.
I will try and I report to you the result.