C#•5mo ago

Entity Framework 6 error - 'Value cannot be null. Parameter name: entitySet'

This piece of code is throwing the above error:

using (var dbContext = new ApplicationDbContext())
 {
                    var x = dbContext.WarningTypes.ToList(); <-- throws entitySet null 
                    ...
}

using (var dbContext = new ApplicationDbContext())
 {
                    var x = dbContext.WarningTypes.ToList(); <-- throws entitySet null 
                    ...
}

This is my WarningType class:

namespace Domain
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.Linq;

    public class WarningType
    {
        public Guid Id { get; set; }

        [Required]
        [StringLength(200)]
        public string Name { get; set; }

        [Required]
        public string Message { get; set; }
}

namespace Domain
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.Linq;

    public class WarningType
    {
        public Guid Id { get; set; }

        [Required]
        [StringLength(200)]
        public string Name { get; set; }

        [Required]
        public string Message { get; set; }
}

This is my DbSet in ApplicationDbContext.cs:

public virtual DbSet<WarningType> WarningTypes { get; set; }

public virtual DbSet<WarningType> WarningTypes { get; set; }

I attached the database table picture for WarningTypes.

22 Replies

FusedQyou•5mo ago

I don't use EF without Dependency Injection. Judging by this code the connection string is not passed which is required. Consider using DI in your project rather than making a custom instance each time

Skenderbegu•5mo ago

I already have this on ApplicationDbContext:

public ApplicationDbContext()
            : base("name=ApplicationDbContext")
        {
        }

public ApplicationDbContext()
            : base("name=ApplicationDbContext")
        {
        }

And my webconfig contains

<connectionStrings>
      <add name="ApplicationDbContext" connectionString="data source=localhost;initial catalog=DatabaseName;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" />
    </connectionStrings>

<connectionStrings>
      <add name="ApplicationDbContext" connectionString="data source=localhost;initial catalog=DatabaseName;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework" providerName="System.Data.SqlClient" />
    </connectionStrings>

Would it not throw an error in the using statement if the connection string was empty or wrong in that case?

Kouhai•5mo ago

Can you send the full code for WarningType it seems to be a partial class and the code snippet doesn't include everything

Skenderbegu•5mo ago

That's all actually, it's not a partial class, my mistake

leowest•5mo ago

are u working with legacy app?

Kouhai•5mo ago

Hmm, can you attach the full stack trace?

Skenderbegu•5mo ago

Yes, it's a legacy app which was having a few caching issues using some other framework. Now we're changing it to EF6 temporarily until we move to EF core

Skenderbegu•5mo ago

And later on when saving the error log I have the text file below