Angular + Web API Error Only In Production - asp.net-core-webapi

Question

About the App
I have an Angular 8 App that uses .Net REST APIs that I inherited from a previous employee (I am new to both frameworks). It has been under development for a few months and has been successfully published to the Production server for testing several times throughout development.
The Issue
After the last publish to the Production server, I am receiving two errors in the console stating Unexpected token < in JSON at position 0 for the API call api/MtUsers/GetLoggedInUser which is called on the backend of the home component. I did not update any code in the home component or the MTUsersController since the last time changes were published to production.
Observations
Error only appears in production
Error still exists if I checkout an older (previously working) commit and publish
Visual Studio started complaining about experimental decorators and missing modules on publish (fixed by restarting VS)
Calling the API using postman appears to return index.html in production but returns the MtUser object in localhost
What I've Tried
Clean solution and re-publish
Checkout last known working commit and publish
Recycle application pool and restart website in IIS
Try various code changes related to website configuration
Relevant Code
I'm not too sure what is most "relevant" to this issue, so I am providing the code specified in the error and the startup.cs file. Let me know if something else would be more useful.
home.component.ts
import { Component } from '#angular/core';
import { MtUser } from 'src/app/core/models/mtUser.model'
import { MtUserService } from 'src/app/core/services/mtUser.service';
#Component({
selector: 'app-home',
templateUrl: './home.component.html',
})
export class HomeComponent {
loadingLoggedInUserInfo = true;
loggedInUser: MtUser = <MtUser>{};
/** home ctor */
constructor(
private mtUserService: MtUserService){
document.getElementsByClassName('main-content')[0].scroll(0, 0);
this.mtUserService.GetLoggedInUser()
.subscribe(response => {
this.loadingLoggedInUserInfo = false;
this.loggedInUser = response;
});
}
}
MtUserService
import { Injectable } from '#angular/core';
import { MtUser } from 'src/app/core/models/mtUser.model';
import { environment } from 'src/environments/environment';
import { HttpClient } from '#angular/common/http';
#Injectable({ providedIn: 'root', })
export class MtUserService {
constructor(private http: HttpClient) { }
GetLoggedInUser() {
return this.http.get<MtUser>(environment.apiUrl + '/MtUsers/GetLoggedInUser');
}
}
MtUsersController
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using MT8.Data;
using MT8.Models;
using MT8.Utilities;
namespace MT8.Controllers
{
[Authorize]
[Route("api/[controller]")]
[ApiController]
public class MtUsersController : Mt8ControllerBase
{
private readonly Mt8Context _context;
public MtUsersController(Mt8Context context)
{
_context = context;
}
// GET: api/MtUsers/GetLoggedInUser
[HttpGet("GetLoggedInUser")]
public async Task<ActionResult<MtUser>> GetLoggedInUser()
{
var loggedInUserName = ApplicationEnvironment.GetLoggedInUserName(this.HttpContext);
var loggedInUser = await this._context.MtUsers
.SingleOrDefaultAsync(u => u.UserName == loggedInUserName);
if (loggedInUser == null)
return NotFound();
return loggedInUser;
}
}
}
Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.SpaServices.AngularCli;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.EntityFrameworkCore;
using MT8.Data;
using Microsoft.AspNetCore.Server.IISIntegration;
using System.Threading.Tasks;
using MT8.Utilities;
namespace MT8
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
readonly string MyAllowSpecificOrigins = "_myAllowSpecificOrigins";
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllersWithViews();
// In production, the Angular files will be served from this directory
services.AddSpaStaticFiles(configuration =>
{
configuration.RootPath = "ClientApp/dist";
});
services.AddCors(options =>
{
options.AddPolicy(MyAllowSpecificOrigins,
builder =>
{
builder.WithOrigins("http://example.com",
"http://www.contoso.com");
});
});
services.AddDbContext<Mt8Context>(options =>
options.UseSqlServer(Configuration.GetConnectionString("Mt8Context")));
services.AddAuthentication(IISDefaults.AuthenticationScheme);
services.AddControllers()
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToIntJsonConverter()))
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToNullableIntConverter()))
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToDecimalJsonConverter()))
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToDoubleJsonConverter()))
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToDateTimeJsonConverter()))
.AddJsonOptions(options =>
options.JsonSerializerOptions.Converters.Add(new StringToNullableDateTimeConverter()));
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, Mt8Context dbContext)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
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();
if (!env.IsDevelopment())
{
app.UseSpaStaticFiles();
}
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller}/{action=Index}/{id?}");
});
app.UseSpa(spa =>
{
// To learn more about options for serving an Angular SPA from ASP.NET Core,
// see https://go.microsoft.com/fwlink/?linkid=864501
spa.Options.SourcePath = "ClientApp";
if (env.IsDevelopment())
{
spa.UseAngularCliServer(npmScript: "start");
}
});
if (!env.IsProduction())
dbContext.InitializeData();
}
}
}

Answer 1

After lots of trial and error, I determined the issue was with a connection string in the appsettings.Production.json file. It was originally set to Integrated Security=True
when the application was first built and something caused this to stop working all of a sudden. I updated the database to use an SQL login and provided the ID and password in the connection string which fixed the issue.