Swagger UI showing "Fetch error Not Found" - swagger

Question

in my asp.net core 2.1 api I have added static files serving and Swashbuckle, but apparently can't find the generated .json
services.AddSwaggerGen(x =>
x.SwaggerDoc("Swagger", new Info { Title = "Asp.Net Core 2 Api", Description = "Swagger Core Api" }));
----
app.UseCors("AllowAll");
app.UseAuthentication();
app.UseStaticFiles();
app.UseSwagger();
app.UseSwaggerUI(x => x.SwaggerEndpoint("/swagger/swagger.json", "Core Api"));
any idea? thanks

Answer 1

Your swagger end-point has the wrong Url, hence the 'Not Found' Error.
Swagger documents constructed via the default way have their url in the format /swagger/<document-name>/swagger.json where is the name (first string) parameter supplied in the call to x.SwaggerDoc("Swagger", new Info {...});
In your case you supplied "Swagger", hence your endpoint url should be "/swagger/Swagger/swagger.json".
and in your ConfigureServices your call should be like
app.UseSwaggerUI(x => x.SwaggerEndpoint("/swagger/Swagger/swagger.json", "Core Api"));

Answer 2

After publishing the application on IIS,
I had this same problem, here is how I solved it.
In the Startup.cs file Add in the public void ConfigureServices(IServiceCollection services)... method
services.AddSwaggerGen();
services.AddSwaggerGen(options =>
{
options.SwaggerDoc("OpenAPISpec",
new OpenApiInfo()
{
Title = "Your Title here",
Version = "1",
Description = "A simple example ASP.NET Core Web API",
TermsOfService = new Uri("https://example.com/terms"),
Contact = new OpenApiContact()
{
Email = "youremail#gmail.com",
Name = "Jean Fritz DUVERSEAU",
Url = new Uri("https://www.rezo509.com")
}
});
var xmlCommentFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
var xmlCommentsFullPath = Path.Combine(AppContext.BaseDirectory, xmlCommentFile);
options.IncludeXmlComments(xmlCommentsFullPath);
});
and then in the public void Configure(... method
app.UseSwagger();
app.UseSwaggerUI(s =>
{
string swaggerPath = string.IsNullOrWhiteSpace(s.RoutePrefix) ? "." : "..";
s.SwaggerEndpoint($"{swaggerPath}/swagger/OpenAPISpec/swagger.json", "Demo API");
});
After that execute the project, then in the browser modify the url as follows:
http (s): //yourserver.com:[port]/swagger/index.html
if you dont add the correct url you will have HTTP ERROR 404
And after publication on the IIS server

Answer 3

Long story short: you must check the path prefix difference on your environments and reflect this difference in SwaggerEndpoint([different path]) option.
One of convenient ways is to automate this difference is to put this selection to #if DEBUG section

Answer 4

this worked for me
`
public void ConfigureServices(IServiceCollection services)
{
services.AddSwaggerGen(c =>
{
c.SwaggerDoc("v1", new OpenApiInfo
{
Title = "Test API",
Version = "v1",
Description = "List of Api's.",
Contact = new OpenApiContact
{
Name = "Test site",
Email = string.Empty
},
});
});
services.AddCors();
services.AddHttpContextAccessor();
services.AddSingleton<Microsoft.AspNetCore.Http.IHttpContextAccessor, HttpContextAccessor>();
services.AddControllers();
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint("v1/swagger.json", " API V1");
c.RoutePrefix = "swagger";
});
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
`
Try copy pasting your application link om a browser
e.g. http://localhost/testsite/swagger/v1/swagger.json
compare it with the link in the error.
Tweak the url in c.SwaggerEndpoint accordingly