How to Use ValueInjecter with Asp.net MVC ViewModel ?

What is ValueInjecter ?

• An Open Source Free product
• It's a Mapper
• It lets you define your own convention-based matching algorithms (ValueInjections)
• In order to match up (inject) Source values to Destination values
• With the ValueInjecter you inject values from the properties of source into properties of target object using ValueInjections
• Each ValueInjection has it's own conventions of which properties to match and how to transform the value.
• By Default maps the properties with the Same Name and Same Type
• But you can override TypesMatch to change this from source to the ones in the target
                                                                                                                   

When To Use ?

• When we need to Map Domain Model to ViewModel and Vice-versa

How to Download?

• You can download the "Omu.ValueInjecter.dll" from CodePlex located Here

How to Set Reference for above .dll on Your Project ?

• On your Web Project Add Reference to the "Omu.ValueInjecter.dll"

Let's Try with Simple Example

• C# , MVC 3 and Visual Studio 2010 has been used.
• Please Follow an Inline Comments on Code.
• Simple application with Product Name text box,Retail Price text box and Save button.   

       
Our Simple View Looks Like below

Our Domain Model Looks like below

 public class Product

    {

        public Product() { Id = Guid.NewGuid() //create Guid as Primary key }

        public Guid Id { get; set; }

        public string ProductName { get; set; }

        public decimal RetailerPrice { get; set; }

       

        public virtual Provider Provider { get; set; }

    }

Our ViewModel Looks like below

public class ProductViewModel

    {

        public Guid Id { get; set; }

        [Required(ErrorMessage = "required")]

        public string ProductName { get; set; }

        [Required(ErrorMessage = "required")]

        public decimal RetailerPrice { get; set; }

             

    }

Our Controller Looks like below

        [HttpPost]

        public ActionResult AddProduct(ProductViewModel productViewModel, string providerKey)

        {

            //get provider from repository

            var provider = Repository.GetProvider(providerKey);

            //create Product domain object

            var productObj = new Product();

            //usage of ValueInjecter

            //source object as productViewModel

            //target object as productObj

            //type 'FilterId' for keep target property 'Id' value

            //not overridden from source property 'Id' value (will explain later)

            productObj.InjectFrom<FilterId>(productViewModel);

            //If something missing then map as below

            productObj.Provider = provider;

            if (ModelState.IsValid) //check validation

            {

                //save for repository

                Repository.AddProduct(productObj);

                return RedirectToAction("AddProduct", new { providerKey = providerKey });

            }

            else

            {

                return View(productViewModel);

            }

        }

Our FilterId  Custom Class Looks like below

using Omu.ValueInjecter;

namespace PawLoyalty.Web.Areas.Providers.ValueInjections

{

    public class FilterId : LoopValueInjection

    {

        //sourcePropName "Id" will not map to target property name "Id"

        //ie: Keep target property value as it is (not change from mapping)

        protected override bool UseSourceProp(string sourcePropName)

        {

            return sourcePropName  !=  "Id";

        }

    }

}

Why We Need 'FilterId' Custom Class ?

# It's a Custom class inherited from LoopValueInjection class

# On our Domain Model (Product) we have to Initialize property Id of type Guid when creates

   an object (inside a constructor) as a Primary Key.

# So After that generated Id will save on the Database at the end

# When we use productObj.InjectFrom(productViewModel) Line of code (default)
   Without <FilterId> then source object (productViewModel) will override the

   target  object's Id with value {00000000-0000-0000-0000-000000000000}.

# So for avoid such a situation we have to use FilterId Custom class as above

#  i.e When we need to keep without changing target property Id value (productObj).
          Because it is our Primary key.

What Says Creator of ValueInjecter ? - By Valentin Plamadeala

Another way of doing the FilterId injection would be like this:

Method 1:
     
public class FilterId : ConventionInjection

 {

   protected override bool Match(ConventionInfo c)

    {

      return c.SourceProp.Name != "Id" && c.SourceProp.Name == c.TargetProp.Name

             && c.SourceProp.Type == c.TargetProp.Type;

    }

 }

Method 2 :

public class IngnoreProps : ConventionInjection

    {

        private readonly string[] _ignores;

        public IngnoreProps()

        {

        }

        public IngnoreProps(params string[] ignores)

        {

            _ignores = ignores;

        }

        protected override bool Match(ConventionInfo c)

        {

            return (_ignores == null || !_ignores.Contains(c.SourceProp.Name)) &&

                   c.SourceProp.Name == c.TargetProp.Name

                   && c.SourceProp.Type == c.TargetProp.Type;

        }

    }

and use it like this:

    target.InjectFrom(new IgnoreProps("Id"), source);

Special Thanks

I must put special thanks for Valentin Plamadeala (Creator of ValueInjecter) who gave me a feedback for my Article and also put that on codeplex. Thanks Valentin.I hope you will create lots of this kind of value added components behalf of us in future also.Good Luck.

What are the Features of ValueInjecter ?

• It's Simple and Very Flexible
• It's something like mozilla with it's plugins, you create ValueInjections and use them
• There are built-in injections for flattening, unflattering
• Can use with MVC ,Win-Forms,Web-Forms,Silverlight,WPF and Data Access Situations
• Can also use ValueInjecter to map from Anonymous and Dynamic objects
• Valueinjecter has a default injection .InjectFrom() that does the properties with the Same Name and Same Type.
• For everything else you can Create your Custom Valueinjections with individual mapping logic/rules, more like aspects. e.g. from all properties of Type Foo to all properties of type Bar

                 What is Aspects - Aspect Oriented Programming (AOP) involves breaking down

                                               program logic into distinct parts.

Do you need to Dive Deep ends of  ValueInjecter ?

• Documentation Here

• Discussions  Here

• Stackoverflow  Here

Conclusion

• Above I have showed very simple usage of ValueInjecter Mapper
• If you need to learn more about ValueInjecter then you have to follow above mentioned Links
• This mapper is nicely fit with Asp.Net MVC ViewModel developments for very simple to very complex scenarios

I hope this helps to You.Comments and feedback greatly appreciated.

Happy Coding.

Related Article

How to Use ViewModel with ASP.NET MVC ?