I am new to EF core and I'm trying to get it to work with my ASP.NET Core project.
I get the above error in my startup.cs when trying configure the DbContext to use a connection string from config. I am following this tutorial.
The problematic code is in startup.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.SpaServices.Webpack;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.EntityFrameworkCore;
using tracV2.models;
using tracV2.data;
namespace tracV2
{
public class Startup
{
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
// Add framework services.
services.AddMvc();
services.AddSingleton<IConfiguration>(Configuration);
string conn = Configuration.GetConnectionString("optimumDB");
services.AddDbContext<tracContext>(options => options.usesqlserver(conn));
}
The UseSqlServer method is recognized if I put it directly into the context:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
namespace tracV2.data
{
public class tracContext : DbContext
{
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer("myrealconnectionstring");
}
All my research online points to missing references, but I can't seem to find out which one I am missing (see image).
First we install the Microsoft.EntityFrameworkCore.SqlServer NuGet Package:
PM > Install-Package Microsoft.EntityFrameworkCore.SqlServer
Then, after importing the namespace with
using Microsoft.EntityFrameworkCore;
we add the database context:
services.AddDbContext<AspDbContext>(options =>
options.UseSqlServer(config.GetConnectionString("optimumDB")));
adding
using Microsoft.EntityFrameworkCore;
manually solved the problem for me
Found that here
Edit...
for dotnet core 3.1 add
Microsoft.EntityFrameworkCore.SqlServer
Follow the steps below.
Install Entity Framework Core Design and SQL Server database provider for Entity Framework Core:
dotnet add package Microsoft.EntityFrameworkCore.Design
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
Import Entity Framework Core:
using Microsoft.EntityFrameworkCore;
And configure your DbContext:
var connectionString = Configuration.GetConnectionString("myDb");
services.AddDbContext<MyDbContext>(options =>
options.UseSqlServer(connectionString)
);
Install below NuGet Package will solve your issue
Microsoft.EntityFrameworkCore.SqlServer
Install-Package Microsoft.EntityFrameworkCore.SqlServer
EntityFramework UseSqlServer Solved
Install-Package Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore
Install-Package Microsoft.EntityFrameworkCore.SqlServer
I believe this can be solved by adding a project reference to Microsoft.EntityFrameworkCore.SqlServer.Design
Install-Package Microsoft.EntityFrameworkCore.SqlServer.Design
Microsoft.EntityFrameworkCore.SqlServer wasn't directly installed in my project, but the .Design package will install it anyway as a prerequisite.
The Package is missing. Open Package Manager Console and execute the code below:
Install-Package Microsoft.EntityFrameworkCore.SqlServer
your solution works great.
When I saw this video till 17 Minute: https://www.youtube.com/watch?v=fom80TujpYQ
I was facing a problem here:
services.AddDbContext<PaymentDetailContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("DevConnection")));
UseSqlServer not recognizes so I did this
Install-Package Microsoft.EntityFrameworkCore.SqlServer -Version 3.1.5
&
using Microsoft.EntityFrameworkCore;
Then my problem is solved. About me: basically I am a purely PHP programmer since beginning and today only I started .net coding, thanks for good community in .net
Install the following packages from Nuget :-
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Sqlite.Core
I was using Visual Studio Code.
1) Try to install the package 'Microsoft.EntityFrameworkCore.SqlServer' by specifying the version number.
VS Code:
'dotnet add package Microsoft.EntityFrameworkCore.SqlServer -v 1.1.1'
Visual Studio:-
'Install-Package Microsoft.EntityFrameworkCore.SqlServer -v 1.1.1'
Refer the link 'Package 'Microsoft.EntityFrameworkCore.SqlServer' is incompatible with 'all' frameworks in the project' for doing it.
2) Then add the namespace 'using Microsoft.EntityFrameworkCore;' manually in the Startup.cs file.
Refer the below link
https://github.com/aspnet/EntityFramework/issues/7891.
3) If you get any dependency issue for 'Microsoft.EntityFrameworkCore.SqlServer.Design', like "Package 'Microsoft.EntityFrameworkCore.Design' is incompatible with 'all' frameworks in project" ,we need to run the below command,
VS Code:-
dotnet add package Microsoft.EntityFrameworkCore.Design -v 1.1
Visual Studio
Install-Package Microsoft.EntityFrameworkCore.Design -v 1.1
Project -> ManageNugetPackages -> Browse -> Search "Microsoft.EntityFrameworkCore.SqlServer" and install or update.
As mentioned by top scoring answer by Win you may need to install Microsoft.EntityFrameworkCore.SqlServer NuGet Package, but please note that this question is using asp.net core mvc. In the latest ASP.NET Core 2.1, MS have included what is called a metapackage called Microsoft.AspNetCore.App
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/metapackage-app?view=aspnetcore-2.2
You can see the reference to it if you right-click the ASP.NET Core MVC project in the solution explorer and select Edit Project File
You should see this metapackage if ASP.NET core webapps the using statement
<PackageReference Include="Microsoft.AspNetCore.App" />
Microsoft.EntityFrameworkCore.SqlServer is included in this metapackage. So in your Startup.cs you may only need to add:
using Microsoft.EntityFrameworkCore;
In Visual Studio, check the NuGet Package Manager => Manage Packages for Solution, check all this packages, whether got installed in your solution or not, as below:
EntityFrameworkCore
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.InMemory
Microsoft.EntityFrameworkCore.Relational
Microsoft.EntityFrameworkCore.Sqlite.Core
Microsoft.EntityFrameworkCore.SqlServer
Microsoft.EntityFrameworkCore.Tools
I solved the same issues after check all the above packages have been installed.
Install package, EntityFrameworkCore.SqlServer:
PM> Install-Package Microsoft.EntityFrameworkCore.SqlServer -Version 3.1.3
Nuget:
https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.SqlServer/
I also had the same problem. I added the following. It works for me
Microsoft.EntityFrameworkCore.SqlServer
In my case :-
I have hit the below command and it is resolved.
Command
Install-Package Microsoft.EntityFrameworkCore.SqlServer -v 1.1.1
I add SqlServer and Sqlite to my project, the same problem arises.
For me, I installed Microsoft.EntityFrameworkCore earlier, it's version is 5.0.6. Now Microsoft.EntityFrameworkCore.SqlServer version is 5.0.7. There is no UserSqlServer method after installation.
1. Try to upgrade the tool version to be consistent
Try to modify the version in csproj:
<PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.7">
Or open NuGet to update the package.
2. Restart your Visual Studio
If it won't help you, the most important thing is to restart VS
And then, everything is OK.
reference
https://github.com/dotnet/efcore/issues/7891
For me this issue happened with Visual Studio Code and I was able to fix with 2 steps:
Manually adding using Microsoft.EntityFrameworkCore;
Running dotnet build in terminal.
first add Install-Package Microsoft.EntityFrameworkCore.SqlServer
next add in your .cs file using Microsoft.EntityFrameworkCore;
finally add this in your core Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddEntityFrameworkSqlServer().AddDbContext<ApplicationContext>(options => options.UseSqlServer(Configuration.GetConnectionString("MovieContext")));
}
For anyone still having this problem:
Use NuGet to install:
Microsoft.EntityFrameworkCore.Proxies
This problem is related to the use of Castle Proxy with EFCore.
Wow so many answers yet none mentioned this Microsoft.EntityFrameworkCore.InMemory package!
Add the reference to this package:
<PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="2.2.2" /> and you should be good to go.
If you are facing this issue in case of Sqlite then
.
I think this is the problem with version of Sqlite,I had the same problem when I was using this versions of SqLite
Version 2.2.4:
After checking version here I changed the version then it worked.
No error after using this
Version 2.1.2:
Easy way to fix this issue
Error message:
Solution:
to install "microsoft.entityframeworkcore.sqlserver" with NuGet
Fixed :
PS: make sure you have using EF on the content "using Microsoft.EntityFrameworkCore;"
I read and did everything instructed in every answer and I just found out my problem was a missing constructor on my DbContext
public Context(DbContextOptions<Context> options) : base(options) { }
I hope this helps anyone facing the same problem I was.
I got around this by simply:
Add SqlServerDbContextOptionsExtensions to the class in question
Resolve SqlServerDbContextOptionsExtensions
This fixes the issue, must be missing some reference by default.
I had this trouble when I moved to Microsoft.EntityFrameworkCore.SqlServer v3.0.0 and Microsoft.EntityFrameworkCore.Tools v3.0.0
When I changed back to v2.2.6 on both libraries, the error went away. This is more of a workaround than a solution but it'll get you up and running till the issue is fixed.
Currently working with Entity Framework Core 3.1.3. None of the above solutions fixed my issue.
However, installing the package Microsoft.EntityFrameworkCore.Proxies on my project fixed the issue. Now I can access the UseLazyLoadingProxies() method call when setting my DBContext options.
Hope this helps someone. See the following article:
Lazy Loading in EF Core
For asp.net core version 2.1 make sure to add the following package to fix the problem. (At least this fix the issue using SQLite)
dotnet add package Microsoft.EntityFrameworkCore.Sqlite
dotnet add package Microsoft.EntityFrameworkCore.Design
Here is the reference of the documentation using SQLite with entity framework core.
https://learn.microsoft.com/en-us/ef/core/get-started/netcore/new-db-sqlite
I had this issue, it seems that I hadn't added the required NuGet packages, although I thought I had done so, make sure to check them, one by one.
Install-Package:
**Microsoft.EntityFrameworkCore.SqlServer**
then add the top of your class:
**Microsoft.EntityFrameworkCore;**
that's worked for me
I'm working on one of those new "Class Library (NuGet Package)" projects in Visual Studio. Everything was going fine until the other day it started raising an error about a:'assembly 'EntityFramework.Core, Version=7.0.0.0 reference??
How can I install the 7.0 version of EntityFramework into my Nuget packages??
"This issue" says that you need to add a reference to:
assembly 'EntityFramework.Core, Version=7.0.0.0
You can solve it by running the following command in the Package Manager Console:
Install-Package EntityFramework.Core -Pre
The issue is the EF version is different and following 2 assemblies are not supported.
using System.Data.Objects;
using System.Data.Objects.DataClasses;
Comment the above 2 lines and the following line in the code behind of your .edmx
using System.Data.Entity.Core.Objects;
I added all SignalR component but I still have got some errors about dll recognition.
The type or namespace name 'Hub' could not be found (are you missing a using directive or an assembly reference?)
I added following libraries on NuGet;
Microsoft.ASpNet.SignalR
Microsoft.ASpNet.SignalR.Client
Microsoft.ASpNet.SignalR.Core
Microsoft.ASpNet.SignalR.JS
Microsoft.ASpNet.SignalR.OWin
Microsoft.ASpNet.SignalR.SystemWeb
Microsoft.Owin
Microsoft.Owin.Host.SystemWeb
Microsoft.Owin.Security
I think, I don't need most of them.
namespace GenelProject
{
[HubName("gsChat")]
public class ChatHub : Hub
Why Visual Studio doesn't recognize SignalR hub when I want to use it ?
You only need the Microsoft.AspNet.SignalR.Core package. And make sure you have the namespace Microsoft.AspNet.SignalR imported with a using statement in your file.
please right click on your project and select manage Nuget Packages then in Installed tab find Microsoft.ASPnet.signalR press uninstall. then try installing it again.
We are using EPPlus to generate Excel documents. Code builds successful in my local system but it is failing when we build through TeamCity and getting below error -
error CS0246: The type or namespace name 'OfficeOpenXml' could not be found (are you missing a using directive or an assembly reference?)
I have tried Google to find the solution but all in vain. My Project target framework is 4.5.2 and I have also added System.Core and WindowsBase. I have also added namespace "using OfficeOpenXml"
EPPlus is added through Nuget Package.
If you have any packages installed using NuGet, then you need to add a NuGet Installer build step in your build configuration before the actual build command, using the solution file which references the NuGet packages you need. This step is what causes TeamCity to download any NuGet packages that are required that it doesn't have installed.
I solved it by removing and add EPPlus reference manually.
I'm getting this error with my Visual Studio 2012, Console App (it is a self-hosted webApi OWIN project)....
The type or namespace name 'Configuration' does not exist in the namespace
'WebApiContrib.Formatting.Html' (are you missing an assembly reference?)
The error is coming from this line ...
using WebApiContrib.Formatting.Html.Configuration;
I'm also getting a similar error for ...
using WebApiContrib.Formatting.Html.Formatters;
using WebApiContrib.Formatting.Html.Locators
In the project references I can see...
WebApiContrib.Formatting.Html
Any ideas how I can fix it please?
According to the documentation the HtmlMediaTypeViewFormatter type, and probably others, are found in WebApiContrib.Formatting.Html.Formatting. You don't need the Configuration namespace.
Check if you have installed all necessary packages and the latest version by using the NuGet package manager:
PM> Install-Package WebApiContrib.Formatting.Html