Cannot add DbContext ASP.Net Core or access data using controllers

Question

I created a context using Scaffold-DbContext

Scaffold-DbContext "Server=******.database.windows.net;Database=first_choice_main; User ID = ****; Password=****" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models\Azure\Main

It created the following Context in the Models\Azure\Main folder:

namespace firstChoicePortal.Models.Azure.Main
{
    public partial class First_choice_mainContext : DbContext
    {
        public virtual DbSet<BlobsDetails> BlobsDetails { get; set; }
        public virtual DbSet<BranchInfo> BranchInfo { get; set; }
        public virtual DbSet<BranchMatrix> BranchMatrix { get; set; }
        public virtual DbSet<CommEventLog> CommEventLog { get; set; }
        public virtual DbSet<CommEventTypes> CommEventTypes { get; set; }
        public virtual DbSet<ContainerEvents> ContainerEvents { get; set; }
        public virtual DbSet<ContainerEventTypes> ContainerEventTypes { get; set; }
        public virtual DbSet<Containers> Containers { get; set; }
        public virtual DbSet<ContainerScans> ContainerScans { get; set; }
        public virtual DbSet<Customers> Customers { get; set; }
        public virtual DbSet<Drivers> Drivers { get; set; }
        public virtual DbSet<ExcludedPoints> ExcludedPoints { get; set; }
        public virtual DbSet<FilesToFtp> FilesToFtp { get; set; }
        public virtual DbSet<FtpEventLog> FtpEventLog { get; set; }
        public virtual DbSet<IncomingTngReturnScans> IncomingTngReturnScans { get; set; }
        public virtual DbSet<ItemTypes> ItemTypes { get; set; }
        public virtual DbSet<LinehaulTracker> LinehaulTracker { get; set; }
        public virtual DbSet<MaintEventTypes> MaintEventTypes { get; set; }
        public virtual DbSet<NewgisticsScans> NewgisticsScans { get; set; }
        public virtual DbSet<OutgoingUpdateQueue> OutgoingUpdateQueue { get; set; }
        public virtual DbSet<PodDetail> PodDetail { get; set; }
        public virtual DbSet<PodUpdatesSentDetail> PodUpdatesSentDetail { get; set; }
        public virtual DbSet<PodUpdatesSentMaster> PodUpdatesSentMaster { get; set; }
        public virtual DbSet<PointMaintEvents> PointMaintEvents { get; set; }
        public virtual DbSet<ProgramSettings> ProgramSettings { get; set; }
        public virtual DbSet<ReceiveScanEventTypes> ReceiveScanEventTypes { get; set; }
        public virtual DbSet<ReceiveScanLog> ReceiveScanLog { get; set; }
        public virtual DbSet<ReceiveScans> ReceiveScans { get; set; }
        public virtual DbSet<RepAssignedStopMatrix> RepAssignedStopMatrix { get; set; }
        public virtual DbSet<RepInfo> RepInfo { get; set; }
        public virtual DbSet<ScanTypes> ScanTypes { get; set; }
        public virtual DbSet<StopAddressDetails> StopAddressDetails { get; set; }
        public virtual DbSet<StopEventLog> StopEventLog { get; set; }
        public virtual DbSet<StopEventTypes> StopEventTypes { get; set; }
        public virtual DbSet<SystemsConfiguration> SystemsConfiguration { get; set; }
        public virtual DbSet<Table> Table { get; set; }
        public virtual DbSet<TestData> TestData { get; set; }
        public virtual DbSet<TestLh> TestLh { get; set; }
        public virtual DbSet<TngRmaItems> TngRmaItems { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
                optionsBuilder.UseSqlServer(@"Server=*****.database.windows.net;Database=first_choice_main; User ID = *****; Password=*****");
            }
        }

I then created a controller using the right-click method and choosing "API Controller with actions, using EF".

This is the first part of it:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using firstChoicePortal.Models.Azure.Main;

namespace firstChoicePortal.Controllers
{
    [Produces("application/json")]
    [Route("api/RepInfoApi")]
    public class RepInfoApiController : Controller
    {
        private readonly First_choice_mainContext _context;

        public RepInfoApiController(First_choice_mainContext context)
        {
            _context = context;
        }

        // GET: api/RepInfoApi
        [HttpGet]
        public IEnumerable<RepInfo> GetRepInfo()
        {
            return _context.RepInfo;
        }

If I run this and go to https://localhost:44325/api/RepInfoApi I get:

InvalidOperationException: Unable to resolve service for type 'firstChoicePortal.Models.Azure.Main.First_choice_mainContext' while attempting to activate 'firstChoicePortal.Controllers.RepInfoApiController'.

So I thought maybe I needed to add this to my services in startup, I added:

services.AddDbContext < First_choice_mainContext> (options =>
options.UseSqlServer(Configuration.GetConnectionString("AuzureConnectionMain")));

But I now get a runtime error right at start up of:

"System.ArgumentException: 'AddDbContext was called with configuration, but the context type 'First_choice_mainContext' only declares a parameterless constructor. This means that the configuration passed to AddDbContext will never be used. If configuration is passed to AddDbContext, then 'First_choice_mainContext' should declare a constructor that accepts a DbContextOptions<First_choice_mainContext> and must pass it to the base constructor for DbContext.'"

Am I going about this the wrong way?

UPDATE AND EXPLANATION ON SOLUTION

I had a couple things missing / wrong, and as Nkosi pointed out the error message did contain the solution. But it is a bit deeper than that. What I was trying to do was to use a connection string pulled from the appsettings.json file. The tooling works 100% as it, but it hard codes your connection information directly in the datacontext with this bit of code:

 protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
                optionsBuilder.UseSqlServer(@"Server=******.database.windows.net;Database=first_choice_main; User ID = ******; Password=******");
            }
        }

As you can see, MS recommends removing this code and replacing it with a connection string based solution - which I almost did correctly. Almost did not quite cut it -- thanks to the SO community once again!

Nkosi · Accepted Answer · 2018-05-13 02:13:24Z

4

The exception message spells out exactly what you need to do

'AddDbContext was called with configuration, but the context type 'First_choice_mainContext' only declares a parameterless constructor. This means that the configuration passed to AddDbContext will never be used. If configuration is passed to AddDbContext, then 'First_choice_mainContext' should declare a constructor that accepts a DbContextOptions<First_choice_mainContext> and must pass it to the base constructor for DbContext.

Emphasis mine

Follow the instructions and add the constructor

public partial class First_choice_mainContext : DbContext {


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

    //...
}

That way the context can be resolved correctly when injecting into dependent classes.

answered May 13, 2018 at 2:13

Nkosi

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2 Comments

Joe Ruder Over a year ago

Thank you - I will accept this answer as it 100% fixes the problem. I do not understand why the default tooling does not / did not create this? Was there something I should have done differently with my Scaffold-DbContext command? I don't recall having to manually modify my context I have created before, but I have been working with Postgresql before vs sql server.

Joe Ruder Over a year ago

OK...I was confused as to why the tooling did not create this in the first place. I will update my question to reflect what I have learned in case anybody else trips up over this.

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