MVVM Broker Castle Interceptor FUN

Posted on 2 mins read

Scenario: have a WPF application based on custom MVVM + Broker + Castle, the users told us that some operations took long time to accomplish and they want a wait cursor on the application.

Resolution: Since all long operations are triggered with event handled by a Broker system, the obvious solution is an interceptor

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public class WaitCursorInterceptor : IInterceptor
{
private IWpfSystem _wpfSystem;
 
public WaitCursorInterceptor(IWpfSystem wpfSystem)
{
_wpfSystem = wpfSystem;
}
 
public void Intercept(IInvocation invocation)
{
using (_wpfSystem.SetWaitCursor())
{
invocation.Proceed();
}
}
}

This depends on the IWpfSystem interface that has this function to change the cursor of the application

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public DisposableAction SetWaitCursor()
{
Mouse.OverrideCursor = Cursors.Wait;
return new DisposableAction(() => Mouse.OverrideCursor = null);
}

Now you only need to wire up everything adding the interceptor on the IBroker interface.

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ServiceLocator.FluentRegistration(
Component.For<WaitCursorInterceptor>());
 
ServiceLocator.FluentRegistration(
Component.For<IWpfSystem>()
.ImplementedBy<WpfSystem>());
 
ServiceLocator.FluentRegistration(
Component.For<IBroker>()
.ImplementedBy<Broker>()
.Interceptors(new InterceptorReference(typeof(WaitCursorInterceptor))).Anywhere);

Now every call to broker function pass through the interceptor that automatically set the cursor to wait. Then users told us that some views take a long time to open and they want the cursor to appear when a new view waits to appear.

Since all view are created/managed by the navigator, you only need to write this.

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ServiceLocator.FluentRegistration(
Component.For<INavigator>()
.ImplementedBy<MainNavigator>()
.Interceptors(new InterceptorReference(typeof(WaitCursorInterceptor))).Anywhere);

Add the same interceptor on the INavigator interface, and the game is done.

alk.