Wednesday, 30 September 2015

Introduction

      This post is a continuation of [Article] WPF Wizard control with MVVM support. Here I am trying to address some of the concerns people have regarding wizard control. This include
1. How to share/collect data from each view.
2. How to control the navigation or how to validate before navigation.

To know more on the basics, please refer to the parent article. Here I have modified the wizard control files. The wizard comes with three files.

This control comes in three files.

1. Wizard.cs
2. WizardItemHeader.cs
3. IWizardItem.cs

You can download this control from Here.



public interface IWizardItem
    {
        /// <summary>
        /// This method should return the header for wizard item to display
        /// </summary>
        /// <returns> A string value.</returns>
        string GetHeader();

        /// <summary>
        /// This method will be the first to get invoked even before the OnViewActivated call. This method will pass a shard object to views in wizard where they can collect the shared object.
        /// </summary>
        /// <param name="sharedObject">
        /// This is the shared object. This will contain information from other views in the wizard.
        /// </param>

        void CollectSharedObject(object sharedObject);

        /// <summary>
        /// This method will be invoked to check whether this item can be displayed or not.
        /// </summary>
        /// <returns>A boolean value indicating true or false status</returns>

        bool CanDisplay();

        /// <summary>
        /// This method will get invoked when the wizard item becomes the active item.
        /// </summary>
        /// <param name="autoAcknoledgeNext">
        /// The auto Acknoledge Next. Setting this to true will help wizard skip this view and take you to the next page automatically.
        /// </param>

        void OnWizardItemNavigatedTo(ref bool autoAcknoledgeNext);

        /// <summary>
        /// This method will get invoked on the current wizard item when the control is moved to next wizard item.
        /// </summary>
        /// <param name="canNavigateAway">
        /// The can Navigate Away. This value when set to false, will not allow navigation from this view. You can use this to do some validation before you navigate to next view.
        /// </param>

        void OnWizardItemNavigatedFrom(ref bool canNavigateAway);
    }

IWizardItem is the interface which you need to implement on the viewmodel for the view which you will show in the wizard. Here wizard also exposes a property called “SharedObject” this can be of any type which. The wizard will then pass it to the viewmodel of the view currently displayed. So the viewmodel can collect it and save data on to this and can be used at later stage.

Now you can use this wizard in wpf as shown below.
<wizardView:Wizard CancelCommand="{Binding CancelCommand}"
      OkCommand="{Binding OkCommand}"
      SharedObject="{Binding SharedObject}"       
      Orientation="Top"
      FinalButtonText="Done"
      WizardItems="{Binding WizardItems}" />

You can download the sample code from Here.