C#•8mo 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•8mo 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

SkenderbeguOP•8mo 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•8mo ago

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

SkenderbeguOP•8mo ago

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

leowest•8mo ago

are u working with legacy app?

Kouhai•8mo ago

Hmm, can you attach the full stack trace?

SkenderbeguOP•8mo 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

SkenderbeguOP•8mo ago

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

message.txt

SkenderbeguOP•8mo ago

But I don't think the text file is really important because the provided Id at that point is not an actual user

Kouhai•8mo ago

I assume you didn't run migration or anything,the db already exists right?

SkenderbeguOP•8mo ago

Yes, the db already exists

Kouhai•8mo ago

What's the table name?

SkenderbeguOP•8mo ago

WarningTypes I also tried adding the attribute [Table("WarningTypes")] to the WarningType class But still got the same error

Kouhai•8mo ago

Hmmm, have you tried specifying the Id as a Key with the attribute Key?

SkenderbeguOP•8mo ago

Just tried a second time to make sure, but still got the same error

Kouhai•8mo ago

Can you change StringLength to MaxLength?

SkenderbeguOP•8mo ago

Same error still

Kouhai•8mo ago

I guess the best bet is to enable ef logging and see what's the generated sql

SkenderbeguOP•8mo ago

This is all I'm getting:

TEST DEBUG ++++++++++++++++++++++++++++++++++++++++++++
'iisexpress.exe' (CLR v4.0.30319: /LM/W3SVC/2/ROOT-1-133576509696931889): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\System.Data.OracleClient\v4.0_4.0.0.0__b77a5c561934e089\System.Data.OracleClient.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Exception thrown: 'System.ArgumentNullException' in EntityFramework.dll
An exception of type 'System.ArgumentNullException' occurred in EntityFramework.dll but was not handled in user code
Value cannot be null.

TEST DEBUG ++++++++++++++++++++++++++++++++++++++++++++
'iisexpress.exe' (CLR v4.0.30319: /LM/W3SVC/2/ROOT-1-133576509696931889): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\System.Data.OracleClient\v4.0_4.0.0.0__b77a5c561934e089\System.Data.OracleClient.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Exception thrown: 'System.ArgumentNullException' in EntityFramework.dll
An exception of type 'System.ArgumentNullException' occurred in EntityFramework.dll but was not handled in user code
Value cannot be null.

SkenderbeguOP•8mo ago

seems to throw the same error even running a simple query such as:

dbContext.Database.ExecuteSqlCommand("Print 'TEST'");

dbContext.Database.ExecuteSqlCommand("Print 'TEST'");

Kouhai•8mo ago

I'm honestly not sure what's causing that, maybe ask in #database They'd be more knowledgable about EF

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