CODEWITHSUNDEEP
c#asp.net-mvcentity-framework
King_Fisher
King_Fisher

Reputation: 1213

Cannot implicitly convert type 'System.Collections.Generic.List<MODEL#1>' to 'System.Collections.Generic.List<Model#2>

I'm using MVC5 with EF6 .I'm getting the below conversion Error

Cannot implicitly convert type System.Collections.Generic.List<TreaceabilitySystem.GLB_M_PROFITCENTER> to System.Collections.Generic.List<TreaceabilitySystem.Models.Profitcenter>

        private TSEntities db = new TSEntities();
        // GET: Profitcenter
        public ActionResult Index()
        {

            List<Profitcenter> profitcenter = new List<Profitcenter>();

            profitcenter = db.GLB_M_PROFITCENTER.ToList(); //Error coming up here

            return View(profitcenter.ToList());
        }

My models are here: This Model created through EF when i add table in .edmx

 public partial class GLB_M_PROFITCENTER
        {
            [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
            public GLB_M_PROFITCENTER()
            {
                this.GLB_M_USERMASTER = new HashSet<GLB_M_USERMASTER>();
            }

            public string PROFITCENTER_CODE { get; set; }
            public string PROFITCENTER_NAME { get; set; }
            public string DESCRIPTION { get; set; }
            public bool ISACTIVE { get; set; }
            public int CREATEDBY { get; set; }
            public System.DateTime CREATED_DATE { get; set; }
            public Nullable<int> UPDATEDBY { get; set; }
            public Nullable<System.DateTime> UPDATED_DATETIME { get; set; }

            [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
            public virtual ICollection<GLB_M_USERMASTER> GLB_M_USERMASTER { get; set; }
        }

And I have created the below model for change the display name and validation purposes 

 [MetadataType(typeof(Profitcenter))]
    public partial class GLB_M_PROFITCENTER { }

     public class Profitcenter
        {
            [Required(ErrorMessage = "*")]
            [DisplayName("Profitcenter Code")]
            public string PROFITCENTER_CODE { get; set; }
            [Required(ErrorMessage = "*")]
            [DisplayName("Profitcenter Name")]
            public string PROFITCENTER_NAME { get; set; }


            [DisplayName("Description")]
            public string DESCRIPTION { get; set; }

            [DisplayName("Is Active")]
            public bool ISACTIVE { get; set; }

            [DisplayName("Created By")]
            public int CREATEDBY { get; set; }

            [DisplayName("Created Timestamp")]
            public System.DateTime CREATED_DATE { get; set; }

            [DisplayName("Upated by")]
            public Nullable<int> UPDATEDBY { get; set; }

            [DisplayName("Updated Timestamp")]
            public DateTime UPDATED_DATETIME
            {
                get; set;
            }
        }

both models are exactly same , Am I missing anything ? How do I fix this?

Upvotes: 1

Views: 2811

Answers (4)

vgru
vgru

Reputation: 51224

Some programming languages, unlike C# and other C-like languages, allow for what is called "duck typing", which would let you assign from different types if they both "quack the same way".

In C#, however, you can only assign an instance of a class to a variable of the same type, or of a base type (a class which your class extends, or an interface which it implements). Even if you had two classes which looked exactly the same, you wouldn't be able to assign from one of them to the other. .NET prior to version 4.0 didn't even support proper generic covariance and contravariance, meaning you couldn't even assign a IEnumerable<Tderived> to IEnumerable<Tbase> even if Tderived is derived from Tbase.

The solution could be to:

  1. use a tool which will map from one class to the other (i.e. copy between equally named properties), like AutoMapper, or

  2. redesign your app to have a separate assembly which contains common entities to be shared between other assemblies type (not a bad idea either), or

  3. extract an interface so that you can assign to this base interface.

It is not uncommon to use mapping to resolve this issue, since you often want to have plain data transfer objects for moving data between tiers, so using an automated tool for this is ok, but if you can keep all entities in a separate assembly which is referenced by both DAL and business layer, but doesn't know anything about them, then it's an even better approach because it avoids any runtime mapping issues.

Upvotes: 1

CodeCaster
CodeCaster

Reputation: 151594

both models are exactly same

That doesn't mean you can just assign the one to the other. For this code to work:

Foo foo = new Foo();
Bar bar = foo;

Bar must be a base type of Foo. This isn't the case here, both your Bar and Foo just happen to have the same property names.

You need to map from one to the other:

public Profitcenter Map(GLB_M_PROFITCENTER input)
{
    return new Profitcenter
    {
        PROFITCENTER_CODE = input.PROFITCENTER_CODE,
        ...
    };
}

You can do the mapping of the entire list with Select():

List<Profitcenter> profitcenter = new List<Profitcenter>();
profitcenter = db.GLB_M_PROFITCENTER.Select(Map).ToList();

An automated way of doing this could be using AutoMapper, which works especially well if all properties on both sides are named identically.

That only answers your question partially though. You have two types: GLB_M_PROFITCENTER, an Entity Framework-generated class that represents a database table, and Profitcenter, where you have added attributes that can be used for input validation using the MetadataType attribute.

I'm not a fan of the latter, because you're then using Entity Framework models as viewmodels for your UI layer. You shouldn't, and you can just remove the MetadataType attribute from the partial class definition.

So you can either use the MetadataType, but then never really instantiate that type (after all, it is a metadata type):

List<GLB_M_PROFITCENTER> profitcenter = db.GLB_M_PROFITCENTER.ToList();
return View(profitcenter);

And make your view @model IEnumerable<GLB_M_PROFITCENTER>. Then MVC will read the MetadataType attribute for GLB_M_PROFITCENTER, and apply the metadata (DisplayName, ...) as applied to Profitcenter (but you shouldn't).

Or you can simply apply mapping, thereby decoupling your view model from your entity model (and thus your database), with all additional benefits.

Upvotes: 5

David McEleney
David McEleney

Reputation: 3813

If the member names are the same - use auto mapper - it will automatically convert each type. 

Mapper.CreateMap<SourceType, DestinationType>()

Then you can call 

Mapper.Map<DestinationType>(instanceofSourceType);

Upvotes: 0

Stanislav Šolc
Stanislav Šolc

Reputation: 305

GLB_M_PROFITCENTER and Profitcenter are not same types, you just share metadata for sharing of attributes from viewmodel to entity model. You should use linq projection for conversion of one type to other

db.GLB_M_PROFITCENTER.select(e => new Profitcenter() {
     /* props mapping*/
}).ToList()

you can also use mapping engine for example AutoMapper

Upvotes: 0

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