The type or namespace name 'Entity' does not exist in the namespace 'System.Data'

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I'm using WS class and it gave me error when I run the application:

The type or namespace name 'Entity' does not exist in the namespace 'System.Data'

I have a reference to the System.Data; and to System.Data.Entity; But no changes. I keep getting the error. I have also in the web.config the line:

<compilation debug ="true" targetFramework="4.0"/>

Jaxartes answered 2/4, 2012 at 7:30 Comment(7)

In the object browser for the System.Data assembly, are you seeing this Entity namespace? Also see if your referring to the correct version of the framework library. System.Dll is 4.0V – Patter 2/4, 2012 at 7:32

Have you installed Entitiy framework? Coz i believe it belongs to that package. – Patter 2/4, 2012 at 7:38

you think so? but I use the same code in another project and it works fine! – Jaxartes 2/4, 2012 at 7:43

Hmm.. Sorry i was wrong. Googling, i found this link. Hope it helps? forums.asp.net/t/1195753.aspx/1 – Patter 2/4, 2012 at 7:49

System.Date.Entity namespace makes sense only with EntityFramework.dll referenced. – Armil 2/4, 2012 at 7:58

EntityframeWork.dll where is it? in the Net tab when I add a reference? – Jaxartes 2/4, 2012 at 8:38

When trying to use EF 6.4.4 in a .NET Standard 2.0 project (still transitioning to .NET 8) I was able to resolve this by adding this to any project file that needs ef: <ItemGroup> <Reference Include="EntityFramework"> <HintPath>..\packages\EntityFramework.6.4.4\lib\net45\EntityFramework.dll</HintPath> </Reference> </ItemGroup> – Watson 5/2 at 17:14

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Thanks every body! I found the solution. not that I understand why but I tried this and it worked! I just had to add a reference to: System.Data.Entity.Design and don't have to write any using in the code. Thanks!

Jaxartes answered 2/4, 2012 at 9:43 Comment(2)

After upgrading to EF 6.1 I had to add a reference to System.Data.Entity, not the Design... – Esthonia 9/4, 2014 at 20:13

DO not add the DESIGN reference! The only reason it worked is that includes a dependency on System.Data.Entity, which is the correct reference as @DeanKuga said – Mayoralty 3/4, 2015 at 15:20

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Right-click on the Solution from the Visual Studio Solution Explorer click the Manage Nuget packages for solution and install the EntityFramework

Wakashan answered 4/8, 2014 at 18:6 Comment(5)

(Including automatically doing everything for you that the other answers state). – Arrive 29/12, 2014 at 0:49

The accepted answer was correct for me, as I already had EntityFramework installed and it was the upgrade to a new version that caused this issue for me. – Guglielma 26/2, 2015 at 15:37

A StackOverflow answer to how to install Entity Framework for dummies (like me). – Francklyn 11/9, 2015 at 13:55

I already had it installed, but I did an "Update-Package -reinstall" and it resolved my issue – Diazonium 21/12, 2015 at 18:31

In my case the compilation errors did not disapear until I build again the project. – Harlem 22/11, 2021 at 18:15

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Hi this post is very misleading, if your reading this 2 years on.

With using EF6 and .net 4.5.1 in VS 2013 I have had to reference the following to get this to work

using System.Data.Entity.Core.EntityClient;

a little different to before,

this is more of a FYI for people that come here for help on newer problems than a answer to the original question

Ratchet answered 8/7, 2014 at 9:12 Comment(2)

If 'Entity' doesn't exist in System.Data, then how do you reason that System.Data.Entity.Core.EntityClient will work? – Ambala 9/2, 2016 at 17:43

This is specific to EF 6.3+ where the introduced the Core part of the namespace (see the docs) – Fanjet 15/5, 2020 at 21:3

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Thanks every body! I found the solution. not that I understand why but I tried this and it worked! I just had to add a reference to: System.Data.Entity.Design and don't have to write any using in the code. Thanks!

Jaxartes answered 2/4, 2012 at 9:43 Comment(2)

After upgrading to EF 6.1 I had to add a reference to System.Data.Entity, not the Design... – Esthonia 9/4, 2014 at 20:13

DO not add the DESIGN reference! The only reason it worked is that includes a dependency on System.Data.Entity, which is the correct reference as @DeanKuga said – Mayoralty 3/4, 2015 at 15:20

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I had entity framework 6.1.3, upgraded (well, more downgraded in NuGet) to 6.1.2. Worked.

Cluck answered 17/4, 2016 at 13:59 Comment(1)

I did the downgraded and worked, I was opening an old code and that was it. – Giralda 26/1, 2018 at 20:24

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Most of the answers here seem to lack awareness of the namespace change that happened between EF 6.2 and 6.3.

I was intentionally upgrading from EF 6.1 to 6.3 to be able to target .NET Standard 2.1. However, I accidentally used .NET Standard 2.0 for the new target in my lib and then got the The type or namespace name 'Entity' does not exist in the namespace 'System.Data'. This GH issue comment gave me the clue I needed to fix. I changed my lib target to .NET Standard 2.1 and the project compiled. No re-installs, uninstalls, or restarts were required.

Fanjet answered 15/5, 2020 at 23:45 Comment(0)

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You need to install Entity framework by right click on your VS solution and click Manage NuGet Package solution and search there Entity framework. After installation the issue will be solved

Leavetaking answered 3/11, 2016 at 6:10 Comment(0)

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I will add my answer to cover all cases:

My solution was unistalling EntityFramework from NuGet Package Manager and then I was prompted to restart Visual Studio because it couldn't "finalize the uninstall".

I restarted Visual Studio and reinstalled EntityFramework then my problem was solved.

Hope this helps someone!

Prepuce answered 5/5, 2016 at 13:25 Comment(1)

hmmm.. Uninstalling and re-installing worked for me as well.. !! – Frogmouth 27/9, 2018 at 6:11

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I just had the same error with Visual Studio 2013 and EF6. I had to use a NewGet packed Entity Framework and done the job perfectly

Amongst answered 8/3, 2015 at 18:18 Comment(0)

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Make sure you have the EntityFramework Nuget package installed for your project.

From @TonyDing's answer:

Right-click on the Solution from the Visual Studio Solution Explorer click the Manage Nuget packages for solution and install the EntityFramework

Once it is installed, I still had the error, but then did a reinstall per @papergodzilla's comment:

Update-Package -reinstall

and it resolved my issue

Do this in the Package Manager Console (View > Other windows > Package Manager Console).
Now everything is good!

Dowager answered 10/9, 2018 at 12:19 Comment(1)

Hi all! In my case, this is the post that worked for me. In my solution I had 5 projects that after pulling from our repo were all messed up. Usually rebuilding the project restores the packages, but it wasn't having it and I was left with dozens of broken references and hundreds of errors. Nuget Package Manager said the missing resources were already installed, so I opened the console and ran the -reinstall command and every error went away. Thanks! – Mollee 26/2, 2019 at 22:49

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I installed EntityFramework 6.2 instead of 6.3 and it worked.

Perhaps it is the .NetCoreApp v2.1 or .NETFramework v4.6.1.

Atronna answered 26/11, 2019 at 19:21 Comment(1)

No it's because the 6.2 to 6.3 bump included namespace changes. You don't need to downgrade if you update the namespaces. See the docs – Fanjet 15/5, 2020 at 21:34

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My solution was simple! I was actually having this error when checked out a repo from a svn server. I took following steps to remove error

Cleaned solution
Went to nuget package manager and uninstalled the entity framework.
Removed DataModel and its .cs components.
Shutdown the VS and opened again.
Installed Entity Framework and Recreated entity model.
Check if there is any files needed "Include in the solution". It worked like a charm

Govan answered 28/9, 2018 at 5:2 Comment(0)

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tried reinstall - no luck. i had to refresh a table in my model before it would find Entity.

Nevsa answered 4/3, 2016 at 12:49 Comment(0)

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It's helped me, I uninstalled EF, restarted VS and I added 'using':

using System.Data.Entity;
using System.Data.Entity.Core.Objects;
using System.Data.Entity.Infrastructure;

Ochrea answered 19/5, 2017 at 14:22 Comment(0)

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I had to refresh my DBModel. That solved it

Larrup answered 25/7, 2017 at 9:25 Comment(0)

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I had to reference System.Data.DataSetExtensions, which seems completely illogical

Beggar answered 17/8, 2017 at 9:51 Comment(0)

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I found the root cause is when you install the nuget packages through the UI the scripts won't run sometimes. So I'd recommend open Output view while you do that. If you don't see the license agreement window when installing Nuget, there is a better change your IDE isn't doing the job right. So that's why a restart, cleanup and rebuild helps!

PS: That adding anything under System.Data.Entity.* helps because, that triggers the Nuget installer to work properly. But this I found a quite unreliable way.

So just watch the output window, you MUST see something like a successful nuget installation message at the end. Most the time when there an issue, Nuget installer won't even kick off. That's when your restart of IDE is going to help.

When things go well, Nuget package manager and IDE (I used Installer term above) would do the change, compile the solution and keep you happy! But when its not give a little help by restarting IDE and watching that Output window!

Punic answered 24/5, 2019 at 4:36 Comment(0)

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If you are using EF version more than 6.x , then see if you have installed the entity framework nuget package in every project of your solution. You might have installed Ef but not in that particular project which you are working on.

Stefanistefania answered 13/10, 2019 at 13:35 Comment(0)

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I had the same errors.

I added System.Data.Entity.Repository from Nuget Packages and the errors disappears.

Hope it wil help!

Capstan answered 28/8, 2018 at 14:38 Comment(0)

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I noticed that in the csproj the framework entity had hintpath like

<HintPath>..\..\..\..\..\..\Users\{myusername}

I had this in the nuget.config file:

 <config>
 <add key="repositoryPath" value="../lib" />
 </config>

a) I removed the above lines, b) uninstalled the framework entity package, c) THEN CLOSED THE solution and reopened it, d) reinstalled the framework.

It fixed my issue.

Shellback answered 11/9, 2018 at 15:11 Comment(0)

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If you're using a database-first approach:

Before uninstalling / reinstalling Entity Framework, first try simply adding another table / stored procedure to your model (assuming there are any currently unmapped). That fixed the issue for me. Of course if you don't need the resource mapped then just delete it from the model afterwards. But it looks like a force-regeneration of the edmx did the trick.

Supernova answered 26/2, 2019 at 22:59 Comment(0)

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For those using vscode make sure that EntityFramework is installed by checking your app.csproj file and weirdly enough check if your file where you're referencing to System.Data.Entity is in the /obj folder.

Epiglottis answered 20/5, 2021 at 13:5 Comment(0)

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Everything was properly installed already for me. I just had to restart Visual Studio a few times before it recognized the package in question was installed and stopped spitting out errors.

Fultz answered 18/1 at 21:35 Comment(0)

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When trying to use EF 6.4.4 in a .NET Standard 2.0 project (still transitioning to .NET 8) I was able to resolve this by adding this to any project file that needs ef:

<ItemGroup>
  <Reference Include="EntityFramework">
    <HintPath>..\packages\EntityFramework.6.4.4\lib\net45\EntityFramework.dll</HintPath>
  </Reference>
</ItemGroup>

Watson answered 5/2 at 17:17 Comment(0)

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I had just updated my Entity framework to version 6 in my Visual studio 2013 through NugetPackage and add following References:

System.Data.Entity,
System.Data.Entity.Design,
System.Data.Linq

by right clicking on references->Add references in my project. Now delete my previously created Entity model and recreate it again,Built solution. Now It works fine for me.

Mekka answered 8/9, 2015 at 7:23 Comment(0)

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