Unable to create an object of type 'ApplicationDbContext'. For the different patterns supported at design time

Question

I face the following error when adding the migration of database in .net core

This is the error:

This is the code in Startup:

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<ApplicationDbContext>(options => 
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
           
    services.AddDefaultIdentity<ApplicationUser>().AddEntityFrameworkStores<ApplicationDbContext>();
    services.AddControllers();
}

This is the ApplicationDbContext class:

public class ApplicationDbContext : IdentityDbContext
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
    { }

    public DbSet<ApplicationUser> applicationUsers { get; set; }
}

This is the ApplicationUser:

public class ApplicationUser : IdentityUser
{
    [Required]
    [Column(TypeName = "nvarchar(150)")]
    public string UserFName { get; set; }
    [Required]
    public string UserLName { get; set; }
}

Answer 1

You are trying to run an incorrect dependency injection.

Instead of this...

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

modify to this...

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

or this...

var connection = builder.Configuration.getConnectionstring("DefaultConnection");

builder.Services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(connection));

Answer 2

After spending 2 hours, it turned out that there was one wrong character in the middle of my db password in connection string :(

Answer 3

In my case, I had to delete old snapshot and migration. Steps I took were:

1. Right-click on Migrations folder
2. Open folder in File Explorer
3. Select & Delete all

Answer 4

I had this same problem, this error can appear for many reasons but for my case was because of removing something in program.cs class (startup.cs in older than dotnet 6) and I removed

builder.Services.AddControllersWithViews();

accidently and when added this to my class the error fixed I hope this help you

Answer 5

In My Case in MS Visual Studio2022 .Net 6 reinstall NuGET Packages

1. Microsoft.EntityFrameworkCore Version 6.0.12

2. Microsoft.EntityFrameworkCore.Design Version 6.0.12

3. Microsoft.EntityFrameworkCore.SqlServer Version 6.0.12

4. Microsoft.EntityFrameworkCore.Tools Version 6.0.12

Alter My DbContext ..

using Leagues.Models.Domains;
using Microsoft.EntityFrameworkCore;

namespace Leagues.Models.Context {
    public partial class FifaDbContext:DbContext {
        public FifaDbContext()
        {

        }
        public FifaDbContext(DbContextOptions options):base(options)
        {
        
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder); 
        }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder); 
        }
        public virtual DbSet<League> Leagues { get; set; }
        public virtual DbSet<Club> Clubs { get; set; }
        public virtual DbSet<Point> Points { get; set; }
    }
}

Confirm My AppSettings

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "FiFa": "Data Source=DESKTOP-R34I8VP;Initial Catalog=FiFaWorldCup;Integrated Security=True;"
  }
}

Confirm Program.cs

using Leagues.Models.Context;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
var ConnectionStrings = builder.Configuration.GetConnectionString("FiFa");
builder.Services.AddDbContext<FifaDbContext>(option => option.UseSqlServer(ConnectionStrings));
builder.Services.AddControllersWithViews();



var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();

Add-Migration

Update-Database

Answer 6

In my case I wanted to create the migration from my class library project.

Nuget packages installed:

• Microsoft.EntityFrameworkCore
• Microsoft.EntityFrameworkCore.Design
• Microsoft.EntityFrameworkCore.Tools
• Microsoft.EntityFrameworkCore.SqlServer
  
  All my models and the context are located in that project.
  There is one little detail.
  When you run the migrations the builder is looking for the constructor.
  After digging through the documentation I found this: constructor without parameters
  This is how my DatabaseContext looks like:

public class RandomDataContext : DbContext
{
    public virtual DbSet<YourCustomModel> YourCustomModels { get; set; }

    public RandomDataContext()
    {

    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("your_connection_string");
    }

}

After running this in the package manager console:

dotnet ef migrations add InitialMigration --project YourProjectName

Then

dotnet ef database update --project YourProjectName

I had this problem
And when I solved it, my database was created.

Answer 7

I found that doing the following fixed this for me within my ApplicationDbContext:

public class ApplicationDbContextFactory : IDesignTimeDbContextFactory<ApplicationDbContext>
{
    public ApplicationDbContext CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<ApplicationDbContext>();
        optionsBuilder.UseSqlServer("Server=(LocalDB)\\MSSQLLocalDB;Database={DbName};Trusted_Connection=True;MultipleActiveResultSets=True");
        return new ApplicationDbContext(optionsBuilder.Options);
    }
}

This does appear to be something which changes from user to user.

Answer 8

In my case, this error ocurred when i copied a project from tutorial repository. I managed to solve it by updating the project packages through NuGet Package Manager.

Answer 9

For future reference, a simple gotcha, has got me before.

Make sure you actually have a value inside of the connection string in your appsettings.json file.

I.e.

This will throw an error:

"ConnectionStrings": {
    "ConnectionString": ""
  },

This will not:

"ConnectionStrings": {
    "ConnectionString": "Server=server;Database=db;User Id=user;Password=password!;"
  },

Answer 10

I faced the same problem in .Net 6 Make sure that AddDBContext is above builder.Build

builder.Services.AddDbContext<DatabaseDBContext>(options => 
  options.UseSqlServer(builder.Configuration.GetConnectionString("sqlConnection"))
);
var app = builder.Build();

In the Program.cs file, do not write anything with builder.Services.... below

var app = builder.Build()

line otherwise it throughs an error.

Answer 11

Read this article: https://learn.microsoft.com/en-gb/ef/core/cli/dbcontext-creation?tabs=dotnet-core-cli#from-a-design-time-factory

The tooling tries to create a design-time DB context instance using various methods. One of those methods is to look for an implementation of the IDesignTimeDbContextFactory.

Some of the EF Core Tools commands (for example, the Migrations commands) require a derived DbContext instance to be created at design time in order to gather details about the application's entity types and how they map to a database schema. In most cases, it is desirable that the DbContext thereby created is configured in a similar way to how it would be configured at run time.

Here's how your DB context factory class might look like:

public class ApplicationDbContextFactory : IDesignTimeDbContextFactory<ApplicationDbContext> {
    public BlazorContext CreateDbContext(string[] args) {
        var optionsBuilder = new DbContextOptionsBuilder<ApplicationDbContext>();
        optionsBuilder.UseSqlite("Filename=db.sqlite3");

        return new ApplicationDbContext(optionsBuilder.Options);
    }
}

Answer 12

This might not be your issue, but this is what caused the error on my end. If your app loads an environment variable at build time, that variable should be declared in the terminal. In my case, my app loaded my GOOGLE_APPLICATION_CREDENTIALS from a json file. I needed to export that variable before running anything related to build.

Answer 13

I had two Configurations for Connection Strings in the app settings file, both missing a comma to separate both. When I put the comma, the error was gone.

Answer 14

If you come to this issue while using .Net 6 along with the new minimal hosting model, check that you're not calling builder.build() before calling the AddDbContext on builder.services.

using MyProject.Data;
using Microsoft.EntityFrameworkCore;
var builder = WebApplication.CreateBuilder(args);


// Add services to the container.
builder.Services.AddRazorPages();
string relativePath = ".";
string databasePath = Path.Combine(relativePath, "MyDb.sqlite");


builder.Services.AddDbContext<ApplicationDbContext>(options =>
        options.UseSqlite($"Data Source={databasePath}") //connection string
        );

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}



app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();

app.UseAuthorization();

app.MapRazorPages();

app.Run();

Answer 15

If you are using Docker-Compose project. You need to unload the Docker-Compose project and then clean and rebuild the solution and set the startup project.

It worked for me to create the migration in EFCore.

Answer 16

I faced the same error and when I added this it worked fine:

services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("ConnStr")));
            services.AddScoped<IuserRepositorhy, UserRepository>();

Answer 17

I faced this error when I forgot to do this in Startup.cs.

services.AddTransient<IExcelMasterRepository, ExcelMasterRepository>();

Answer 18

I had three projects, one with Api, second with Models and third with ApplicationDbContext. Api project was starting project. I've added Microsoft.EntityFrameworkCore.Design nuget package to Api project (it's the starting project) and problem solved.

Answer 19

My problem was solved by installing Microsoft.EntityFrameworkCore.Design nuget package.

this package is required for the Entity Framework Core Tools to work. Ensure your startup project is correct.then install the package.

at the end Build -> Clean Solution in your project and then try running your command again.

Help Link

add migration command cli:

dotnet ef migrations add InitDatabase --project YourDataAccessLibraryName -s YourWebProjectName -c YourDbContextClassName --verbose 

update database command cli:

dotnet ef database update InitDatabase --project YourDataAccessLibraryName -s YourWebProjectName -c YourDbContextClassName --verbose

remove migration command cli:

dotnet ef migrations remove --project YourDataAccessLibraryName -s YourWebProjectName -c YourDbContextClassName --verbose

Entity Framework Core tools reference - .NET Core CLI

Answer 20

In my case I was using a custom IdentityErrorDescriber :

  services.AddIdentity<AppIdentityUser, AppIdentityRole>()
              .AddErrorDescriber<MyIdentityErrorDescriber>() // comment this !
              .AddEntityFrameworkStores<MyDbContext>()
              .AddDefaultTokenProviders();

and in my MyIdentityErrorDescriber I was using resources to translate errors. and when I comment out the .AddErrorDescriber<MyIdentityErrorDescriber>() line the migration worked without any errors. I think the problem is either with the IdentityErrorDescriber or Resources.

Answer 21

Thoroughly inspect your appsettings file and endure it is well formed. Lookout fro missing characters or unnecessary characters

Answer 22

Getting the same error...

Here's how I got there:
Created a new ASP.NET Core Web App (Model-View-Controller)
Target Framework was .NET Core 3.1 (LTS)
Authentication Type: Individual Accounts

Once the project was created...I wanted to be able to modify the register/login process.(but these pages are part of the Razor Class Library)
So to get the pages in the project: I right click the project Add->New Scaffolded Item...
And picked Identity...
Next I needed to Add-Migration InitIdentity...and this is where the errors/trouble starts.

I tried reading and working through some of the other answers with no success.
I found a solution by:
Creating the project like (above)
But this time I decided NOT to Scaffold Identity.(yet)
I put a connection string in the application.config and ran the project.
I did this before Add-Migration.
I went in to register...A screen came up and said the migration hasnt run yet and had a button to run the migration. I press it and did a refresh and all was good.
Its at this point I went back to the project and did a Add->Scafolded Item...and now there is no error and I have the Auth screens to modify.

Answer 23

In my case, I was missing a property in appsettings.json that was showing as Warning instead of Error

This error message is sometimes not directly related to the db context model. Check other errors in your Startup class such as missing properties/ credentials in your appsettings.json/ appsettings.Development.json

run your migration with the --verbose option to see all errors and warnings

dotnet ef migrations add YourMigrationName  --verbose

Answer 24

Try This one as of March 2021 - VS 16.9.2

I tried many of the above answers and none worked for me. My issue was that we had multiple startup projects, so that was step one. Just set a single startup project, so I set our Data project to be the startup. Still got the error. Then it hit me (thanks to the @AFetter's answer) the Data project does NOT have a connection string within it. So I set my startup project to one with an appSettings.json file that HAS a connection to the DB and then made sure the Package Manager Console's Default Project was set to the Data project and reran the command to create the migration and it worked!

Answer 25

In my case, this was due to me storing my data types and migrations in a separate "Data" project and accidentally having it set as a startup project rather than my actual startup project.

Answer 26

I found I was missing:

Microsoft.EntityFrameworkCore.Tool
Microsoft.EntityFrameworkCore.Design

I had multiple startup projects (different API's). I was at a different level in the PM console. Then I learned I had to close SQL management so I can run PM console commands.

Answer 27

I had the same error when I had two constructors of my DbContext. After rearranging constructors order to parameterless constructor being first in the class fixed it. e.g.

public ProgramDbContext() : base()
{
}
public ProgramDbContext(DbContextOptions<ProgramDbContext> options) : base(options)
{
}

It must be something with dynamic DbContext object invocation with Reflection playing here.

Answer 28

I also had same problem today when I was running the dotnet ef migrations add <MigrationName>

I had three project, MainApp (Web), C# Project with DBContext and C# Project for Models.

I was able to resolve it from CLI.

dotnet ef migrations add AddCategoryTableToDb -s MainApp -p ProjectHavingDbContext

Answer 29

I was facing the same issue while running the dot net ef migrations script command from the azure pipeline task. I did added "-project" argument. But still was failing. Adding the "-startup-project" argument worked for me. I guess even though we specify startup class in project , for ef tool to find one we have to explicitly mention them.

Answer 30

I had the same error, just modify the program class. Net Core 3.0

    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }
    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });

To

   public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }
    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>() 
            .Build();