How to use PostgreSQL?

I have a ASP.NET Core web application with AspNetCore.Identity Logins. It uses SQL Server for user authentication.

I need to use PostgreSQL database I have added some nuget packages (EF.* etc), changed the connection string and code

 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.UseSqlServer( Configuration.GetConnectionString("DefaultConnection")));
            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseNpgsql( Configuration.GetConnectionString("DefaultConnection")));

            services.AddDefaultIdentity<IdentityUser>()
                .AddEntityFrameworkStores<ApplicationDbContext>();

            services.AddControllersWithViews()
                .AddNewtonsoftJson();
            services.AddRazorPages();
        }

But when I run it, it connects to the PostgreSQL database and tries to create the structure I receive the error, what is wrong? Why EF cannot create the structure? How to solve this problem?

  Executing endpoint 'WebApplication1.Controllers.HomeController.Index (WebA
pplication1)'
info: Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker[3]
      Route matched with {action = "Index", controller = "Home", page = "", area
 = ""}. Executing controller action with signature Microsoft.AspNetCore.Mvc.IAct
ionResult Index() on controller WebApplication1.Controllers.HomeController (WebA
pplication1).
info: Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor[1]
      Executing ViewResult, running view Index.
info: Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor[4]
      Executed ViewResult - view Index executed in 302.6169ms.
info: Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker[2]
      Executed action WebApplication1.Controllers.HomeController.Index (WebAppli
cation1) in 315.3645ms
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'WebApplication1.Controllers.HomeController.Index (WebAp
plication1)'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished in 451.9255ms 200 text/html; charset=utf-8
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 GET https://localhost:5001/Identity/Account/Logi
n
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint '/Account/Login'
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[3]
      Route matched with {page = "/Account/Login", area = "Identity", action = "
", controller = ""}. Executing page /Account/Login
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[101]
      Executing handler method Microsoft.AspNetCore.Identity.UI.V4.Pages.Account
.Internal.LoginModel.OnGetAsync - ModelState is Valid
info: Microsoft.AspNetCore.Authentication.Cookies.CookieAuthenticationHandler[11
]
      AuthenticationScheme: Identity.External signed out.
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[102]
      Executed handler method OnGetAsync, returned result .
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[103]
      Executing an implicit handler method - ModelState is Valid
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[104]
      Executed an implicit handler method, returned result Microsoft.AspNetCore.
Mvc.RazorPages.PageResult.
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[4]
      Executed page /Account/Login in 104.6291ms
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint '/Account/Login'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished in 157.5038ms 200 text/html; charset=utf-8
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 POST https://localhost:5001/Identity/Account/Log
in application/x-www-form-urlencoded 264
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint '/Account/Login'
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[3]
      Route matched with {page = "/Account/Login", area = "Identity", action = "
", controller = ""}. Executing page /Account/Login
info: Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.PageActionInvoker[101]
      Executing handler method Microsoft.AspNetCore.Identity.UI.V4.Pages.Account
.Internal.LoginModel.OnPostAsync - ModelState is Valid
info: Microsoft.EntityFrameworkCore.Infrastructure[10403]
      Entity Framework Core 3.1.0 initialized 'ApplicationDbContext' using provi
der 'Npgsql.EntityFrameworkCore.PostgreSQL' with options: None
fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (182ms) [Parameters=[@__normalizedUserName_0='?
'], CommandType='Text', CommandTimeout='30']
      SELECT a."Id", a."AccessFailedCount", a."ConcurrencyStamp", a."Email", a."
EmailConfirmed", a."LockoutEnabled", a."LockoutEnd", a."NormalizedEmail", a."Nor
malizedUserName", a."PasswordHash", a."PhoneNumber", a."PhoneNumberConfirmed", a
."SecurityStamp", a."TwoFactorEnabled", a."UserName"
      FROM "AspNetUsers" AS a
      WHERE a."NormalizedUserName" = @__normalizedUserName_0
      LIMIT 1
fail: Microsoft.EntityFrameworkCore.Query[10100]
      An exception occurred while iterating over the results of a query for cont
ext type 'WebApplication1.Data.ApplicationDbContext'.
      Npgsql.PostgresException (0x80004005): 42P01: relation "AspNetUsers" does
not exist
         at Npgsql.NpgsqlConnector.<>c__DisplayClass160_0.<<DoReadMessage>g__Rea
dMessageLong|0>d.MoveNext()
      --- End of stack trace from previous location where except

[willdean]

@Oleg26Dev You’re trying to run a “migration” (the script which creates the tables) which was generated for SQL Server, not Postgres. It has a bunch of SQL Server specific stuff which doesn’t run on Postgres.

You need to recreate the migration in such a way as to make a Postgres migration rather than a SQL server one.

Have a look at this comment (and the rest of that issue), which explains what you’re seeing and how to deal with it: https://github.com/npgsql/efcore.pg/issues/404#issuecomment-392942176

[willdean]

@Oleg26Dev You need to create (for Postgres, the SQL server one won’t do) and run the proper “Migration” to create the database. This doesn’t just happen by itself if you’ve taken an existing SQL Server-based project and simply changed the connection string/provider.

This is probably helpful: https://medium.com/@RobertKhou/asp-net-core-mvc-identity-using-postgresql-database-bc52255f67c4