Close a WPF Window using MVVM
In MVVM (Model – View
– ViewModel) design pattern, the ViewModel is a heart of View and this class
that typically contains the values you want to display in your View . ViewModel shouldn’t know anything about the
View.
In this article I will tell you different ways
for closing form in WPF
1.
Using traditional Code Behind Close
event
private void
Close_Click(object
sender, RoutedEventArgs e)
{
this.Close();
}
As you can see, it’s quite simple –
only one line of code that I had to write
2.
Using MVVM design pattern
In
the View of XAML my button:
<Button Content="Close" Command="{Binding CloseCommand}"/>
In
the ViewModel:
public bool CanClose { get; set; }
private RelayCommand
closeCommand;
public ICommand
CloseCommand
{
get
{
if(closeCommand
== null)
(
closeCommand
= new RelayCommand(param
=> Close(), param => CanClose);
)
}
}
public void Close()
{
this.Close();
}
Problem with this solution
All we’ve done here
is move the close button event handler from the code-behind file to the
ViewModel. The problem we run into, As you may be aware, the this
keyword refers to the class in which it exists. This was fine in the
code-behind of the Window, as this then referred to the Window, and
this.Close() would successfully call the window’s Close() method. But now that
we’ve moved the method into the ViewModel, this no longer refers to the
Window (View), but rather the ViewModel – which doesn’t have a Close method.
3.
The Action object.
We will add an Action
property to the ViewModel, but define it from the View’s code-behind file. This
will let us dynamically define a reference on the ViewModel that points to the
View.
Creating
Action
public Action CloseAction { get; set; }
public View()
{
InitializeComponent() // this draws
the View
ViewModel vm = new ViewModel(); //this creates an
instance of ViewModel
this.DataContext = vm; // this sets
the ViewModel as the DataContext for the View
if
( vm.CloseAction == null
)
vm.CloseAction
= new Action(()
=> this.Close());
}
we’ve assigned a delegate to the CloseAction Action property
that we can simply invoke whenever we want to close the Window.
Calling in ViewModel
public void Save()
{
CloseAction();
// Invoke the Action previously defined by the View
}
Using the method described here, we can define the Close
method with a single line on the ViewModel, two lines of code on the View, and
invoke the Close method with a single line making a call to CloseAction().
Happy Programming!!
Don’t forget to leave your feedback and comments below!
Sujeet Bhujbal
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