Creating a view model with a model and mappings with CatelR#

There are tons of yarns based on MVVM developer’s experiences behind Catel framework. Some of them are well documented on Catel docs and one of my favorites is the named "Creating a view model with a model and mappings".

When I started to read it I identified myself as one of those developers that map all the view model properties back to the model.

I will remember you how it started:

"During the use of the MVVM pattern, we noticed that lots and lots of developers have a model, and map the values of the model to all properties of the view model. When the UI closes, the developers map all the properties back to the model. All this redundant code is not necessary when using the view models of Catel." More...

This only feature makes that my interest about Catel grown until I became one of the members of the development team. But this is part of the other history.

Let’s go back to the Catel feature again. If you don’t remember how it works, here is a summary.

Basically if you want to create a model the only thing that you have to do is decorate a view model property with the ModelAttribute. So if you want to expose the model property as view model one, and don’t write the mapping back code you must decorate the exposed property with the ViewModelToModelAttribute just like this:

    /// 

    /// The person view model.
    /// 
    public class PersonViewModel : ViewModelBase
    {
        #region Static Fields

        /// 
Register the FirstName property so it is known in the class.
        public static readonly PropertyData FirstNameProperty = RegisterProperty("FirstName", typeof(string));

        /// 
Register the Person property so it is known in the class.
        public static readonly PropertyData PersonProperty = RegisterProperty("Person", typeof(Person));

        #endregion

        #region Public Properties

        /// 

        /// Gets or sets the first name.
        /// 
        [ViewModelToModel("Person")]
        public string FirstName
        {
            get { return GetValue<string>(FirstNameProperty); }
            set { SetValue(FirstNameProperty, value); }
        }

        /// 

        /// Gets or sets the person.
        /// 
        [Model]
        public Person Person
        {
            get { return GetValue<Person>(PersonProperty); }
            set { SetValue(PersonProperty, value); }
        }

        #endregion
    }

 

This example will automatically create a mapping between Person.FirstName and PersonViewModel.FirstName.

This feature is amazing and Catel distributes some code snippets to accelerate writing such code:

• vm - declare a view model
• vmpropmodel - declare a property as model on a view model
• vmpropviewmodeltomodel - declare a property as a pass-through property on a view model

But could you imagine to yourself writing this code (and more) as fast as is possible (near to the speed of light). Don't you believe me?

Watch the movie, and believe me, it is in slow motion ;)

This is a forthcoming feature of CateR#, now powered by Catel itself.

You got more ideas? Let us know!

Accelerating Catel coding workflow with CatelR#

Overview

The  first release  of ReSharper  (R#)  provoked a  commotion, at  least between my programming  fellowships. Expressions like  "Visual Studio is a great development  tool, but with ReSharper is  awesome" were commonly repeated.

The main reason  of R# success was that the JetBrains team identified a weak point of the Visual Studio coding editor.

Visual Studio, at least in it's firsts versions (.NET versions, 2003, 2005), had no refactoring features,  just like other Java IDEs already had, such as Eclipse or IntelliJ. Also note that  the last two versions of Visual  Studio  improved it's refactoring  features but nothing come close with the power of the R#.

But I will not to talk about R# history, actually the preceding paragraph could be not totally accurate.  I don't  really know how R# was born. (If you know it, don't doubt, just comment it here, allow me to be in the know)

R# as coding workflow guidance

The R#  quick fix  and/or context  action is  very simple  and powerful workflow.  Basically  you can  locate  the  caret  position near  to  an element that  you want to alter, press  Alt + Enter,  and all available suggestions will be displayed. For instance, if you  press Alt + Enter in a  range  corresponding  to  a  "public" modifier  of  a  property,  the suggestions  "To internal", "To  protected" or "To private" would be available, only the options that do not provoke a broken usage are displayed.

 
 {caret}public string FirstName { get; set; }

But all  scenarios are not covered by R#,  there are tons of frameworks and/or toolkit that have it own coding workflows.

Catel coding workflow

If  you are  writing  a WPF  or Silverlight  application  and don't  use Catel, it is  probably that you are not using the right library. See the comparison sheet, for detailed libraries comparison.

But Catel has a "down side". If you want to convert a simple class into a data  or model class in order to  support property changed  notifications and validations, you need re-coding a class like this one:

public class Person
{
 public string FirstName { get; set; }

 public string MiddleName { get; set; }

 public string LastName { get; set; }
}

into this one:

public class Person
{
 public static readonly PropertyData FirstNameProperty = RegisterProperty("FirstName", typeof(string));
 
 public static readonly PropertyData LastNameProperty = RegisterProperty("LastName", typeof(string));
 
 public static readonly PropertyData MiddleNameProperty = RegisterProperty("MiddleName", typeof(string));
 
 public string FirstName
 {
            get { return  this.GetValue<string>(FirstNameProperty); }
            set { this.SetValue(FirstNameProperty, value);  }
 }
 
 public string LastName
 {
            get { return this.GetValue<string>LastNameProperty); }
            set { this.SetValue(LastNameProperty, value); }
 }
 
 public string MiddleName
 {
            get { return this.GetValue<string>(MiddleNameProperty); }
            set { this.SetValue(MiddleNameProperty, value); }
 }
}

As you could be noticed, there is an implementation pattern that should be fully automated. In fact, every Catel version comes with a code snippets package that assist you to write down this class from scratch.

But now, Catel team comes with a new tool. Using the R# SDK, we implement a R# extension that cover the Catel coding workflow and we named CatelR# (obviously).

Now you can do this

You can also do it faster with the R# generation options (Alt + Ins)

The   beta  version,  of CatelR#,  is  released. You can read more about CatelR# and download the beta. We are expecting for your feedback and new features request.

Enjoy it, and have nice coding experience with CatelR#.