Getting "The entity type <model> is not part of the model for the current context."

Question

I am having this issue updating my database 1 column at a time in asp.net using web api. I am trying to query a PUT to just update one value in the row instead of updating that one and setting the rest to null. I made a separate model outside of the controller to take in the update so I could do one at a time. When I hit this line db.Entry(user).State = EntityState.Modified; in the controller that is where it is erroring out. Any advice how I can fix this?

This is my separate ViewModel I am taking in in the put method:

namespace WebAPI.Models.ViewModels
{
    public class UserViewModel
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}

This is my controller calling in the method with the ViewModel in my parameter:

public HttpResponseMessage PutUser(int id, UserViewModel user)
        {
            HttpResponseMessage response;

            if (db.User.IsInRole("Admin"))
            {
                try
                {
                        db.Entry(user).State = EntityState.Modified;
                        db.SaveChanges();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!UserExists(id))
                    {
                        response = new HttpResponseMessage(HttpStatusCode.NotFound);
                        return response;
                    }
                    else
                    {
                        throw;
                    }
                }

                response = new HttpResponseMessage(HttpStatusCode.NoContent);
                return response;
            }

This is my DBContext file:

public partial class Entities : DbContext
    {
        public Entities()
            : base("name=Entities")
        {
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
        public virtual DbSet<User> Users { get; set; }
    }
}

Answer 1

This always happened if your repository needs to dynamic accessing different Entity Framework DbContext which means different databases.

Check your data connection string in web.config file for each Entity Frmework DbContext.

For example:

 <add name="CRMEntities" connectionString="metadata=res://*/CRMEntities.csdl|res://*/CRMEntities.ssdl|res://*/CRMEntities.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=Your Data Source;initial catalog=CRM;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

check metadata in connectionString if it is pointing to a correct DbContext.

In this example, it is pointing to demx file called "CRMEntities".