Entity Framework buddy class results in type conversion error

Question

I have been trying to setup a buddy class (described in this answer) so my annotations I setup on the auto generated Entity Framework classes don't get lost everytime I update the model from the database.

I created the buddy class in the Models directory of my MVC project, The EDMX is in another project in the solution. It fails to compile with this error:

Error CS0029: Cannot implicitly convert type 'TrinityCatalogTool.Data.Details [C:\Projects\Bitbucket\catalog-tool\TrinityCatalogTool.Data\bin\Debug\TrinityCatalogTool.Data.dll]' to 'TrinityCatalogTool.Data.Details [C:\Projects\Bitbucket\catalog-tool\TrinityCatalogTool\Models\Metadata.cs(9)]' (112, 35)

I don't understand why it would fail to cast the original class to my buddy class since the buddy class is a partial of that original. Any idea what I am doing wrong?

This is what my auto generated class looks like:

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated from a template.
//
//     Manual changes to this file may cause unexpected behavior in your application.
//     Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

namespace TrinityCatalogTool.Data
{
    using System;
    using System.Collections.Generic;

    public partial class Details
    {
        public int detail_id { get; set; }
        public int parent_id { get; set; }
        public string short_description { get; set; }
        public string long_description { get; set; }
        public string feature1 { get; set; }
        public string feature2 { get; set; }
        public string feature3 { get; set; }
        public string feature4 { get; set; }
        public string feature5 { get; set; }
        public string feature6 { get; set; }
        public string feature7 { get; set; }
        public string feature8 { get; set; }

        public virtual Parents Parents { get; set; }
    }
}

And this is what my buddy class I created looks like

using System.ComponentModel.DataAnnotations;

namespace TrinityCatalogTool.Data
{
    [MetadataType(typeof(Details.Metadata))]
    public partial class Details
    {
        private sealed class Metadata
        {
            [Display(Name = "Short Description")]
            public string short_description { get; set; }
            [Display(Name = "Long Description")]
            public string long_description { get; set; }
            [Display(Name = "Feature #1")]
            public string feature1 { get; set; }
            [Display(Name = "Feature #2")]
            public string feature2 { get; set; }
            [Display(Name = "Feature #3")]
            public string feature3 { get; set; }
            [Display(Name = "Feature #4")]
            public string feature4 { get; set; }
            [Display(Name = "Feature #5")]
            public string feature5 { get; set; }
            [Display(Name = "Feature #6")]
            public string feature6 { get; set; }
            [Display(Name = "Feature #7")]
            public string feature7 { get; set; }
            [Display(Name = "Feature #8")]
            public string feature8 { get; set; }
        }
    }
}

Thank you, you hit the nail on the head. I moved my buddy class over to the same project as my Entity Framework model and it works now. — Patrick

Patrick Patrick · Accepted Answer · 2016-09-16T18:09:10

Per Siva Gopal's comment, the issue was that my partial class needed to exist in the same project as my auto generated class. When I moved the buddy class to the same project as the original class, it compiled and worked as expected.

Entity Framework buddy class results in type conversion error

1 Answers