The type or namespace name 'DbContext' could not be found

Question

I am VERY new to ASP.NET MVC (3) and am having a hard time resolving a build error in Visual Studio:

The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using System.Data.Entity;

namespace MyProjectName.Models
{   
    public class MachineModel
    {
        // name
        [Required]
        [Display(Name = "Nom de la machine")]
        public string Name { get; set; }

        // IP
        [Required]
        [RegularExpression(@"(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)",
           ErrorMessage = "Donnez une adresse IPv4 valide.")]
        [Display(Name = "Adresse IP de la machine")]
        public string IP { get; set; }
    }

    public class MachineDbContext : DbContext
    {
        public DbSet<MachineModel> Machines{ get; set; }
    }
}

The two errors I am getting are:

The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'DbSet' could not be found (are you missing a using directive or an assembly reference?)

What am I missing?

Did you add the Entity Framework Code First reference using NuGet? That might be the easiest way to resolve references. — Ed Chapel, Apr 21 '11 at 07:54
o.k. - under the Solution Explorer Tree I did a right-click on References -> Add Library Package Reference -> EFCodeFirst -> Install. Is this what you were suggesting? After following these steps I still have the same problem. — Chris, Apr 21 '11 at 09:39
I have meanwhile updated the MVC 3 Tools to the newest version, and created a tutorial project following http://www.asp.net/mvc/tutorials/getting-started-with-mvc3-part4-cs. In that project, I don't have this problem, but I can't get DbContext to be accepted in my older project, despite the suggestions made here and by Darin below... — Chris, Apr 21 '11 at 09:58
VS2017, EF6, Close the solution. Reopen solution. It now properly recognizes DbContext. — redwards510, Aug 03 '17 at 21:18
Open the Package Manager Console. Select Tools > NuGet Package Manager > Package Manager Console. In the Package Manager Console, enter the following command: install-package EntityFramework — Zahid Hasan, Sep 13 '19 at 18:59
Why is this question closed? Thank goodness there are some answers here that helped, before an overzealous mod closed it. — Steve Smith, Mar 05 '20 at 12:40

score 202 · Accepted Answer · answered May 18 '11 at 17:24

202

I had the same issue. Turns out, you need the EntityFramework.dll reference (and not System.Data.Entity).

I just pulled it from the MvcMusicStore application which you can download from: http://mvcmusicstore.codeplex.com/

It's also a useful example of how to use entity framework code-first with MVC.

answered May 18 '11 at 17:24

Shaz

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this was my experience; the EntityFramework.dll for 4.2.0.0 was not present even though the vs2010 Package Manager claimed I had 4.2.0.0 installed. With my project open in vs2010, running the [install command](http://nuget.org/packages/EntityFramework/4.2.0.0) via Tools, Library Package Manager, Package Manager Console added the reference to **EntityFramework** automatically and my subsequent build succeeded. thnx @Shahzad! – gerryLowry Feb 09 '12 at 19:28
7

Thanks for your help. I hope Microsoft would one day make installation of their own software on their windows easier! It is amazing how many places one has to go to to figure what is needed and how they all fit together. NuGet, MS Download site, Message boards, books,....very productive time indeed. – NoChance May 10 '12 at 10:29
24

Your best bet is to use NuGet (package manager) to pull Entity Framework (et al) into your projects. – kingdango Jul 01 '12 at 23:53
2

some times you need to restart visual studio to make the installation works. this was my case. – Bedouin Jun 04 '14 at 10:30
1

You can use the Nuget Manage Packages for Solutions. Find EntityFramework and click Manage. There will be check boxes to where it is installed next to each project. Make sure you are using the version of EF you need. You can use multiple versions in the same solution, for various reasons. – Piotr Kula Mar 06 '15 at 13:44
3

Open Package Manager Console and paste in: Install-Package EntityFramework – user2862542 Jul 27 '15 at 19:49
I had a similar issue after installing the entity framework from Nuget. Rebuilding the solution seemed to sort this out... – wickd Nov 23 '15 at 14:07
1

System.Data.Entity did the trick for me – brntsllvn Jan 07 '16 at 19:26

score 73 · Answer 2 · edited Feb 15 '21 at 09:22

73

You need to reference the System.Data.Entity assembly in your project, or install the EntityFramework NuGet package, which will setup everything for you.

edited Feb 15 '21 at 09:22

Adrian Mole

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answered Apr 21 '11 at 07:54

Darin Dimitrov

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Darin, could you explain how one would do this? – Chris Apr 21 '11 at 09:31
11

@Chris Dickinson, right click on the `References` item in the project and select `Add Reference...`. Then in the `.NET` tab, select `System.Data.Entity`. And if you want to use NuGet, right click on the `References` item and then select `Add Library Package Reference...` and in the Online tab, search for `EntityFramework`. – Darin Dimitrov Apr 21 '11 at 09:33
1

I followed both of your steps, but the problem still persists... – Chris Apr 21 '11 at 09:53
3

did u use NuGet to install EntityFramework?It creates a folder "packages" along side your Solution directory. You will find the "EntityFramework.4.1.10331.0" folder inside it.Within "Libs" folder you will find "EntityFramework.dll" .Add reference to it using Browse tab and select the above dll. see my answer below.. i did the same. – Amitd Jul 10 '11 at 06:31
Required assembly reference is EntityFramework.dll, not System.Data.Entity. I had to do the full Entity Framework 4.1 install to get it - NuGet did not pull the appropriate assembly for me. – mtazva Aug 27 '11 at 23:04
8

I selected `TOOLS > Library Package Manager > Package Manager Console` in VS2012 and typed `install-package EntityFramework` at the prompt. Worked perfectly. – Peter Gluck Dec 04 '13 at 22:24
Only adding the reference to System.Data.Entity still left me with DbContext not being recognized. Also following @PeterGluck his comment worked for me. Small update for VS2017: `>Tools >NuGet Package Manager >Package Manager Console` and type `install-package EntityFramework`. – Kevin Feb 15 '18 at 10:12

score 19 · Answer 3 · answered Oct 23 '11 at 18:34

19

Just a quick note. It is DbContext, not DBContext. i.e. with a lowercase 'B'. I discovered this because I had the same problem while intelesense was not working until I tried typing the full name space System.Data.Entity... and name and finally it suggested the lowercase 'b' option:-

System.Data.Entity.DbContext

answered Oct 23 '11 at 18:34

John Thompson

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I've been going through all the references regarding System.Data.Entity only to discover that the problem was the uppercase "B". +1 – F0r3v3r-A-N00b Jul 14 '15 at 09:35
Yes this solved it. Provided "Install-Package EntityFramework" step was done. Thanks, +1. – Paceman Aug 03 '15 at 10:10

score 11 · Answer 4 · answered Sep 06 '11 at 01:16

11

I had the same problem using VS2010. I know this isn't really an answer. I just thought it might help someone. I resolved it by using the fully qualified name for DBContext.

Instead of

public class MachineDbContext : DbContext

I used

public class MachineDbContext : System.Data.Entity.DbContext

and rebuilt the project. Suddenly VS was happy, and I was even able to remove the fully qualified name, and just use DBContext.

answered Sep 06 '11 at 01:16

cab0

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This worked for me, but it seems very bizarre that I need to fully qualify the DbContext even though the using statement is already in place. Does anyone have any insight on why this is happening? – Fabio S. Nov 11 '21 at 22:05
or Microsoft.EntityFrameworkCore.DbContext - worked for me :) – Eden M May 25 '22 at 14:41

Felipe Skinner · Answer 5 · 2015-10-20T11:14:00.567

9

I had the same issue... Installing the EF from Package Manager Console worked for me

the command was: Install-Package EntityFramework

edited Oct 20 '15 at 11:14

answered Oct 03 '12 at 17:09

Felipe Skinner

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score 5 · Answer 6 · answered Jun 08 '11 at 09:10

If your compiler doesn't recognize

System.Data.Entity.Infrastructure
DbContext
DbSet
et alii,

make sure

you have Entity Framework 4.1 installed on your machine;

in your .csproj file, you have the following reference

<Reference Include="EntityFramework, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL" />

within the element

<ItemGroup>
  ...
</ItemGroup>

that houses references to other assemblies.

score 4 · Answer 7 · edited Jul 01 '12 at 22:57

4

I am using Visual Studio 2010 express and adding a reference to C:\Program Files\Microsoft ADO.NET Entity Framework 4.1\Binaries\EntityFramework.dll solved the problem.

edited Jul 01 '12 at 22:57

Brian Cain

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answered Jul 01 '12 at 13:27

ASHISH

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score 4 · Answer 8 · answered Feb 13 '14 at 05:17

This helps really handy:

Select the ProjectNAme project in Solution Explorer.
From the Tools Menu, choose Library Package Manager which has a sub-menu.
From the sub-menu choose Package Manager Console.
At the console’s PM prompt type install-package EntityFramework then hit enter.

score 4 · Answer 9 · answered Jul 10 '11 at 06:28

I had the same problem..I have VS2010 express..

(Note: If you see this problem try checking references to EntityFramework.dll .. May be it is missing.)

The following resolved it for me.

I installed latest MVC 3 Tools Update
then I installed EntityFramework 4.1
or using NUGet ie. from with Visual Studio 2010 Express (Tools->Library Package Manager -> Add library Package reference -> Select Online -> EntityFramework)

Strangely that didnt work..So i had to manually add a reference to "EntityFramework.dll"
try doing a search for the dll ..may be here
"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework\v4.0\"

If you already have it..just add a '.net' reference.

Note: If you use NuGet ,it creates a folder "packages" along side your Solution directory. You will find the "EntityFramework.4.1.10331.0" folder inside it.Within "Libs" folder you will find "EntityFramework.dll" .
Add reference to it using Browse tab and select the above dll.

Snap for the same

score 3 · Answer 10 · answered Sep 23 '16 at 09:22

Your project unable to resolve EntityFramework classes until you not added it in your project. For adding EntityFramework support you have to follow this steps: Tools->Nuget Package Manager ->Manage Nuget package for solution browse EntityFramework It shows latest stable EntityFramework version. currently 6.1.3 is latest version Install it for the selected project.

score 3 · Answer 11 · edited Jun 03 '17 at 14:43

3

Download http://www.dll-found.com/download/e/EntityFramework.dll

Paste it in (for x86)

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\

Then Right click on project -> add reference -> select EntityFramework

Bingo......

edited Jun 03 '17 at 14:43

Skatox

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answered Jun 03 '17 at 14:17

Sanoop

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score 3 · Answer 12 · answered Apr 21 '11 at 21:55

For step-by-step instructions, see this new MVC / EF tutorial series: http://www.asp.net/entity-framework/tutorials/creating-an-entity-framework-data-model-for-an-asp-net-mvc-application The tutorial assumes you have installed the latest MVC 3 Tools Update and provides a link in case you haven't.

score 2 · Answer 13 · answered Apr 24 '13 at 07:42

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This happened to me when I branched code. To fix it I right-clicked my project in Visual Studio, chose manage Nu-get packages, uninstalled EntityFramework, then re-installed it. Problem solved

answered Apr 24 '13 at 07:42

Neil

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score 2 · Answer 14 · answered Aug 29 '13 at 15:32

I just had this issue and none of the other solutions worked for me. I'm using Visual Studio 2010 and I have two projects in my solution: UIProject and DataAccessProject. The UIProject has a reference to the DataAccessProject.

My UIProject was targeting the .Net Framework 4 but my DataAccessProject was targeting the .Net Framework 3.5 for some reason.

I changed both projects to target .Net Framework 4
Uninstalled then re-installed the Entity Framework NuGet Package.

Problems solved. Now I have references to both EntityFramework and System.Data.Entity

score 2 · Answer 15 · answered Jan 13 '14 at 13:02

i had the same problem.I had to rewrite "DBContext" after adding reference to entityframework and it resolved the problem.
its means that Visual studio was not able to recognize the class automatically and waited for it to be re-typed. so its best to add reference first and then implement code. VS 2013 - ultimate used

score 2 · Answer 16 · answered Dec 07 '15 at 11:40

2

I had to first uninstall EntityFramework(Uninstall-package EntityFramework (not case sensitive apparently)), then install it again(Install-package EntityFramework), via the PM Console

answered Dec 07 '15 at 11:40

Mpilo Z

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score 2 · Answer 17 · answered Jul 25 '11 at 12:32

2

Visual Studio Express SP1 Right click in Solution Explorer > References > Add Library Package Reference > EntityFramework

answered Jul 25 '11 at 12:32

mesteru_vali

21
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score 2 · Answer 18 · answered Oct 18 '11 at 07:14

Use CTP5 instead it is newer version with some changes in API. You have to add reference to EntityFramework.dll which is installed in CTP directory - default is: c:\Program Files\Microsoft ADO.NET Entity Framework Feature CTP5\Binaries\EntityFramework.dll for 32bit system. On 64bit system it will be placed in Program Files (x86).

score 1 · Answer 19 · answered May 30 '12 at 05:26

1

I had this problem, read the above answer and download the entityframework.ddl but found that it is alreadt referenced. So I added the namespace and problem was solved

using System.Data.Entity;

I am using Visual Studio 2010, SP1 installed

answered May 30 '12 at 05:26

Muhammad Waqas Iqbal

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score 1 · Answer 20 · answered Aug 31 '12 at 15:41

1

having referenced entityframework.dll both system.data.entity worked.

answered Aug 31 '12 at 15:41

meol

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score 1 · Answer 21 · answered Oct 04 '12 at 18:11

1

I had the same error but the problem was just an accidental problem with my model.

I accidentaly put...

public class MyModelDBContext : Context
{
 public DBSet<MyModel> MyModels { get; set; }
}

...inside of the model class.

answered Oct 04 '12 at 18:11

Jason Geiger

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Those 3 line actually inside the class? – Nate-Wilkins Oct 04 '12 at 22:59

score 1 · Answer 22 · edited Mar 17 '14 at 14:16

1

Right click your reference and go to manage NuGet packages, then choose online all, then NuGet package source in the search textbox type Entity Framework and install it.

edited Mar 17 '14 at 14:16

Sir l33tname

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answered Jan 12 '14 at 01:16

kidistB

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score 1 · Answer 23 · answered Jan 19 '14 at 16:13

1

As alternative way you can go HERE - instruction how to install any required dll.

Or you can download NuGet and manage it from VS

answered Jan 19 '14 at 16:13

hbk

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score 1 · Answer 24 · answered Oct 21 '14 at 17:49

1

1) Uninstalling Entity Framework from All projects

2) Restart Visual Studio

3) Reinstalling to all required projects

and it started working

answered Oct 21 '14 at 17:49

Moji

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score 1 · Answer 25 · answered Dec 18 '15 at 08:43

There might be a case where you reference everything you need to and you can even Go to Definition by pressing F12 on DbContext class which takes you to System.Data.Entity namespace but you still get this nasty compiler warning. Make sure that the Target Framework of your project and that of the Entity Framework version you are using match. Go to Project->Properties->Application Tab. Change the Target Framework(can't exactly say to which one, trial and error will help.). Just my two cents.

score 1 · Answer 26 · answered Sep 06 '16 at 06:46

1

I also get irritated from this issue many times and finally find the solution.Go to edmx file->Update Model from Database->Refresh->Finish. Clean Solution->Rebuild Solution

answered Sep 06 '16 at 06:46

Aayush Verma

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score 0 · Answer 27 · answered Mar 16 '17 at 07:27

0

you can try on package manager console

PM> EntityFrameWork\enable-migrations

answered Mar 16 '17 at 07:27

Michael Felina

11

score 0 · Answer 28 · answered Dec 05 '17 at 04:58

Like the others have suggested:

Add the correct references and directives. But it still doesn't work? Maybe you have the same problem I did:

Have a look below and see if you can tell me what is wrong:

public class PanelLengthContext : DBContext { } ??!

Make sure the class name is not misspelt - (case sensitivity)!

DbContext is the correct spelling.
this is how it should look:
check the spelling. don't waste 20 min of your life like i did. public class PanelLengthContext : DbContext {}

HTH

score 0 · Answer 29 · answered Feb 01 '18 at 05:14

I have the same issue as you, I'm unable to implement it in the Controller class while it works when I put it in the model class. Add these codes on the top of your controller class

 using TimeSheetManagementSystem.Data;
 using Microsoft.Extensions.Configuration;
 using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore;
 using Newtonsoft.Json;

The type or namespace name 'DbContext' could not be found

29 Answers29

Make sure the class name is not misspelt - (case sensitivity)!

Linked