C#•2d ago

ASP.Net Core Web API unable to connect due to CORS

Hello, I want to call my POST-request through Swagger. Yet when I send the request it gives me the following message and shuts down the application; Undocumented Failed to fetch. Possible Reasons: CORS Network Failure URL scheme must be "http" or "https" for CORS request. I have tried to add CORS into my program.cs but to no avail. How can I solve this, so that I can communicate with my API?

4 Replies

Destination UnknownOP•2d ago

c#
using Asp.Versioning;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.Identity.Web;
using System.Text.Json.Serialization;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));

builder.Services.AddControllers().AddJsonOptions(x =>
{
    x.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
});
builder.Services.AddProblemDetails();
builder.Services.AddApiVersioning(options =>
{
    options.ReportApiVersions = true;
    options.AssumeDefaultVersionWhenUnspecified = true;
    options.DefaultApiVersion = new ApiVersion(1, 0);
    options.ApiVersionReader = new UrlSegmentApiVersionReader();
}).AddApiExplorer(options =>
{
    options.GroupNameFormat = "'v'VVV";
    options.SubstituteApiVersionInUrl = true;
});

builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAll", builder =>
    {
        builder
            .WithOrigins("https://localhost:8080", "http://localhost:8081")
            .AllowAnyHeader()
            .AllowAnyMethod();
    });
});


// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

if (app.Environment.IsStaging() || app.Environment.IsProduction())
{
    app.UseHttpsRedirection();
}

app.UseCors("AllowAll");

app.UseAuthentication();

app.MapControllers();

#pragma warning disable S6966
app.Run();
#pragma warning restore S6966

c#
using Asp.Versioning;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.Identity.Web;
using System.Text.Json.Serialization;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));

builder.Services.AddControllers().AddJsonOptions(x =>
{
    x.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
});
builder.Services.AddProblemDetails();
builder.Services.AddApiVersioning(options =>
{
    options.ReportApiVersions = true;
    options.AssumeDefaultVersionWhenUnspecified = true;
    options.DefaultApiVersion = new ApiVersion(1, 0);
    options.ApiVersionReader = new UrlSegmentApiVersionReader();
}).AddApiExplorer(options =>
{
    options.GroupNameFormat = "'v'VVV";
    options.SubstituteApiVersionInUrl = true;
});

builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAll", builder =>
    {
        builder
            .WithOrigins("https://localhost:8080", "http://localhost:8081")
            .AllowAnyHeader()
            .AllowAnyMethod();
    });
});


// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

if (app.Environment.IsStaging() || app.Environment.IsProduction())
{
    app.UseHttpsRedirection();
}

app.UseCors("AllowAll");

app.UseAuthentication();

app.MapControllers();

#pragma warning disable S6966
app.Run();
#pragma warning restore S6966

appsettings.json: nothing really useful docker-compose.override:

services:
  myProject.api:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - ASPNETCORE_HTTP_PORTS=8080
      - ASPNETCORE_HTTPS_PORTS=8081
    ports:
      - "8080:8080"
      - "8081:8081"

services:
  myProject.api:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - ASPNETCORE_HTTP_PORTS=8080
      - ASPNETCORE_HTTPS_PORTS=8081
    ports:
      - "8080:8080"
      - "8081:8081"

docker-compose.yml

services:
  myProject.api:
    container_name: api
    image: ${DOCKER_REGISTRY-}myProjectapi
    build:
      context: .
      dockerfile: Sample.API/Dockerfile
    ports:
        - "8080:8080"
        - "8081:8081"

services:
  myProject.api:
    container_name: api
    image: ${DOCKER_REGISTRY-}myProjectapi
    build:
      context: .
      dockerfile: Sample.API/Dockerfile
    ports:
        - "8080:8080"
        - "8081:8081"

Without the CORS stuff, you can remove the following lines of the program.cs;

c#
builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAll", builder =>
    {
        builder
            .WithOrigins("https://localhost:8080", "http://localhost:8081")
            .AllowAnyHeader()
            .AllowAnyMethod();
    });
});

app.UseCors("AllowAll");

c#
builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAll", builder =>
    {
        builder
            .WithOrigins("https://localhost:8080", "http://localhost:8081")
            .AllowAnyHeader()
            .AllowAnyMethod();
    });
});

app.UseCors("AllowAll");

Anchy•this hour

I see you have setup your HTTP port as 8080 and your HTTPS port as 8081, however in your CORS settings you have reversed them

Destination UnknownOP•23h ago

Hey Anchy, thank you for your reply. I would assume you mean this line of code:

.WithOrigins("https://localhost:8080", "http://localhost:8081")

.WithOrigins("https://localhost:8080", "http://localhost:8081")

I swapped the 2 but this still gave me the same 'error'

Destination UnknownOP•22h ago

But do i actually need CORS? Because as far as I know, CORS is used when you want to perform HTTP-requests to another domain. In my case everything is local(host). There is something else wrong. I do not get what it can be... it was the fockin browser. I used Brave for this, but brave blocked it. Using Edge works ARGH

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ASP.Net Core Web API unable to connect due to CORS

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