EF Core: 'CS1061: DbContextOptionsBuilder does not contain a definition for UseSqlServer'

error CS1061: 'DbContextOptionsBuilder' does not contain a definition for 'UseSqlServer' and no accessible extension method 'UseSqlServer' ... means the compiler cannot see the SQL Server provider's extension method. Either the project references only Microsoft.EntityFrameworkCore and not Microsoft.EntityFrameworkCore.SqlServer, or the file is missing using Microsoft.EntityFrameworkCore;.

Add the provider package with the same version as your EF Core package. If it is already in the .csproj, add the using directive at the top of the file that calls UseSqlServer. Other providers' methods, such as UseNpgsql, also come from their own packages, so check those first.

The error

  Determining projects to restore...
  All projects are up-to-date for restore.
...\EfLab\Program.cs(6,13): error CS1061: 'DbContextOptionsBuilder' does not contain a definition for 'UseSqlServer' and no accessible extension method 'UseSqlServer' accepting a first argument of type 'DbContextOptionsBuilder' could be found (are you missing a using directive or an assembly reference?) [...\EfLab\EfLab.csproj]

Build FAILED.

The project paths are shortened; nothing else in the output was changed.

Why it happens

UseSqlServer is not a method of DbContextOptionsBuilder. It is an extension method that ships in the provider package, so the core EF Core package alone has nothing by that name. The compiler's hint covers both possible gaps: "a using directive or an assembly reference".

The second gap is easy to hit in an ASP.NET Core project. The package's XML documentation puts AddDbContext in Microsoft.Extensions.DependencyInjection, which is in the project's generated GlobalUsings.g.cs, so that call compiles. The SqlServer package puts UseSqlServer in Microsoft.EntityFrameworkCore, which that file does not list. When the DbContext class is in its own file with its own using and Program.cs has none, the package can be referenced correctly and Program.cs still fails with exactly this CS1061, at the UseSqlServer line and nowhere else.

The fix

dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 10.0.12

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.12" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="10.0.12" />

When the package is there, the fix is the first line of Program.cs:

using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddDbContext<ClinicDb>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("Clinic")));

Both versions built with 0 errors. Keep the provider and the core package on the same version; the provider depends on the core package anyway, so referencing only the provider also works. One thing to know: on this run, adding the SqlServer provider 10.0.12 brought two NuGet audit warnings, NU1902 and NU1903, for a transitive System.Security.Cryptography.Pkcs 9.0.11 (the build summary counted each twice, as 4 warnings). They do not stop the build unless warnings are errors; the NU1903 post shows how to lift a transitive package.

How it was reproduced

A dotnet new web project on .NET SDK 10.0.403 (net10.0) with a ClinicDb context and Microsoft.EntityFrameworkCore 10.0.12 as the only package gave the error above. A second copy with both packages, the DbContext moved to ClinicDb.cs and no using in Program.cs gave the same message at Program.cs(4,13). No database was needed: this is a compile error.

Frequently asked

Which package contains UseSqlServer in EF Core?

Microsoft.EntityFrameworkCore.SqlServer. Add it with dotnet add package Microsoft.EntityFrameworkCore.SqlServer using the same version as your Microsoft.EntityFrameworkCore package.

Why is UseSqlServer not found when the package is installed?

The file is missing using Microsoft.EntityFrameworkCore. ASP.NET Core implicit usings include the namespace of AddDbContext but not the one that holds the provider extension methods.

Do I need both Microsoft.EntityFrameworkCore and the SqlServer package?

No. The SqlServer provider package depends on Microsoft.EntityFrameworkCore, so referencing only Microsoft.EntityFrameworkCore.SqlServer built fine. If you list both, keep them on the same version.

More decoded errors in the Fixes category. If it compiles but fails at run time saying no provider is configured, see No database provider has been configured.