how to use MVVMLight SimpleIoc?

Question

I'm revamping my software which has messy Messenger.Default(...) bits.

Is there any cheat sheet to know MVVMLight SimpleIoc usage (not general IoC description)?

Answer 1

SimpleIoc crib sheet:

1. You register all your interfaces and objects in the ViewModelLocator

   class ViewModelLocator 
   { 
       static ViewModelLocator() 
       {         
           ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);          
           if (ViewModelBase.IsInDesignModeStatic) 
           {              
               SimpleIoc.Default.Register<IDataService, Design.DesignDataService>();          
           }          
           else         
           {              
               SimpleIoc.Default.Register<IDataService, DataService>();          
           }          
           SimpleIoc.Default.Register<MainViewModel>();                  
           SimpleIoc.Default.Register<SecondViewModel>(); 
       }      
   
   
       public MainViewModel Main 
       {  
           get  
           {      
               return ServiceLocator.Current.GetInstance<MainViewModel>();  
           } 
       }
   }
   

2. Every object is a singleton by default. To resolve an object so that it's not a singleton you need to pass a unique value to the GetInstance call:

   SimpleIoc.Default.GetInstance<MainViewModel>(Guid.NewGuid().ToString());
   

3. To register a class against an interface:

   SimpleIoc.Default.Register<IDataService, Design.DesignDataService>();
   

4. To register a concrete object against an interface:

   SimpleIoc.Default.Register<IDataService>(myObject);
   

5. To register a concrete type:

   SimpleIoc.Default.Register<MainViewModel>();
   

6. To resolve an object from an interface:

   SimpleIoc.Default.GetInstance<IDataService>();
   

7. To resolve an object directly (does buildup and dependency resolution):

   SimpleIoc.Default.GetInstance<MainViewModel>();
   

8. MVVM makes doing design-time data really easy:

   if (ViewModelBase.IsInDesignModeStatic) 
   {              
       SimpleIoc.Default.Register<IDataService, Design.DesignDataService>();          
   }          
   else         
   {              
       SimpleIoc.Default.Register<IDataService, DataService>();          
   }
   

If you're in design-time mode it will automatically register your design-time services, making it really easy to have data in your viewmodels and views when working in the VS designer.