无法解决此错误，“尚未为此DbContext配置数据库提供程序”

Question

经过长时间的休息，我最近回到了ASP.Net，并一直在尝试使用Core 2.1开发Web应用程序。

我遵循了Microsoft网站上的“入门”指南之一，并且SQL Express的连接字符串的数据提供程序遇到了问题。

当我尝试访问SQLExpress时，我不断收到错误消息“没有为此DbContext配置数据库提供程序。”>

完整错误

An unhandled exception occurred while processing the request.
InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions<TContext> object in its constructor and passes it to the base constructor for DbContext.
Microsoft.EntityFrameworkCore.Internal.DbContextServices.Initialize(IServiceProvider scopedProvider, IDbContextOptions contextOptions, DbContext context)

Stack Query Cookies Headers
InvalidOperationException: No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions<TContext> object in its constructor and passes it to the base constructor for DbContext.
Microsoft.EntityFrameworkCore.Internal.DbContextServices.Initialize(IServiceProvider scopedProvider, IDbContextOptions contextOptions, DbContext context)
Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
Microsoft.EntityFrameworkCore.DbContext.get_Model()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityType()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityQueryable()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.System.Linq.IQueryable.get_Provider()
Microsoft.EntityFrameworkCore.RelationalQueryableExtensions.FromSql<TEntity>(IQueryable<TEntity> source, RawSqlString sql, object[] parameters)
SQL_Connection_2.Pages.ContactModel.OnGet() in Contact.cshtml.cs
Microsoft.AspNetCore.Mvc.RazorPages.Internal.ExecutorFactory+VoidHandlerMethod.Execute(object receiver, object[] arguments)
Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker.InvokeHandlerMethodAsync()
Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker.InvokeNextPageFilterAsync()
Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker.Rethrow(PageHandlerExecutedContext context)
Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker.InvokeInnerFilterAsync()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
Startup.cs

public void ConfigureServices(IServiceCollection services) {
            services.Configure<CookiePolicyOptions>(options => {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddDbContext<ConfigurationContext>(options => {
                options.UseSqlServer(Configuration.GetConnectionString("MyConnection"));
            });
        }
appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "MyConnection": "server=.\\SQLExpress;database=WebApp_Test;trusted_connection=true;"
  }
}
ConfigurationContext.cs

public class ConfigurationContext:DbContext {

        public ConfigurationContext() { }
        public ConfigurationContext(DbContextOptions options) : base(options) { }


        public DbSet<Person> Persons { get; set; }

    }
[如果我将ConfigurationContext.cs中的代码更改为（以下），一切正常，但是这绕过了appsettings.json中的连接字符串，因此似乎services.AddDbContext在Startup.cs文件中似乎没有执行。] >
public class ConfigurationContext : DbContext {

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {
            optionsBuilder.UseSqlServer(@"Server=.\SQLExpress;Database=WebApp_Test;Trusted_Connection=True;MultipleActiveResultSets=true;");
        }

    }
任何人都可以提供有关如何解决此问题的建议吗？
理想情况下，我希望在appsettings.json文件中配置连接字符串。

我花了很多时间来解决这个问题，寻找发现和学习的机会。

经过长时间的休息，我最近回到了ASP.Net，并一直在尝试使用Core 2.1开发Web应用程序。我遵循了Microsoft网站上的“入门”指南之一，并且...

Answer 1

请尝试使用在OnConfiguring方法中使用的连接字符串，因为发布的内容不同。

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