ICommand & IoC

view-viewmodel.md

@@ -194,4 +194,74 @@ namespace MitechLib.Modules.PackagePage.Views
                {"CarrierInfoView", "MitechLib.Modules.PackagePage.Views.CarrierInfoView"}
             };
 
+```
+
+## Guide to link View command to ViewModel
+
+1. Create `ICommand` variable in view model. Naming convention `<Action>Command`
+
+2. Create `DelegateCommand` to the ICommand within the constructor
+3. Create the Delegate Command callback function
+```cs
+    [Export]
+    public class CarrierInfoViewModel : ViewModelBase, IHeaderInfoProvider<string>
+    {
+        // Step1
+        public ICommand UndoCommand { get; set; }
+
+        [ImportingConstructor]
+        public CarrierInfoViewModel(IRegionManager _regionManager)
+        {
+            // Step2: Initialize ICommand delegate
+            this.UndoCommand = new DelegateCommand(this.OnUndoCommand);
+        }
+
+        // Step3: Callback
+        private void OnUndoCommand()
+        {
+            ConfirmMessageBoxView confirmmessagebox = new ConfirmMessageBoxView("Confirm to undo changes?");
+            confirmmessagebox.ShowDialog();
+            if (confirmmessagebox.DialogResult == false)
+            {
+                return;
+            }
+
+            // TODO: Add Business logic HERE
+            //UpdateWaferInfo(selectedPackage);
+        }
+    }
+```
+
+4. Bind the ICommand to View xaml
+```xml
+
+<Button Content="Undo" Command="{Binding UndoCommand}"/>
+```
+
+## Guide for ViewModel IoC via constructor injection
+1. Attach [ImportingConstructor] to constructor
+2. Assign to a field
+3. Use the object within the class
+```cs
+    [Export]
+    public class CarrierInfoViewModel : ViewModelBase, IHeaderInfoProvider<string>
+    {
+        // Step1
+        public IRegionManager RegionManager { get; }
+
+        // Step2
+        [ImportingConstructor]
+        public CarrierInfoViewModel(IRegionManager _regionManager)
+        {
+            //
+            RegionManager = _regionManager;
+        }
+
+        // Step3
+        private void OnExitCommand()
+        {
+
+            RegionManager.RequestNavigate(RegionNames.PackageMainViewRegion, new Uri("PackageMgmtView", UriKind.Relative));
+        }
+    }
 ```