Access to XMLHttpRequest has been blocked origin ASP.NET CORE 2.2.0 / Angular 8 / signalr1.0.0 [(CORS Policy-Access-Control-Allow-Origin) failed]

You should add your CORS like this:

services.AddCors(options =>
{
    options.AddPolicy("CorsPolicy", builder => builder.WithOrigins("http://localhost:4200")
        .AllowAnyHeader()
        .AllowAnyMethod()
        .AllowCredentials()
        .SetIsOriginAllowed((host) => true));
});

Note:

The order is important!

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