I have set up a ASP.NET Server on localhost.
When I try to fetch data from my WPF Application, it is recieved. But when I also want to fetch the data from my browser, the datastream from the WPF App is interrupted. When I restart the WPF App, the browsers connection is interrupted or the browser is not loading data anymore.

Can you tell me what is wrong?
I did not found any good example of how to set up SSE Connection with WPF.

Please check this video (Left: VS Console, right: Browser)

This is my code of ASP.NET Server:

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.Identity.Web;
using System.Text.Json;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApi(builder.Configuration.GetSection("AzureAd"));

builder.Services.AddControllers();

builder.Services.AddSingleton<ItemService>();
builder.Services.AddCors(options =>
{
    options.AddPolicy("AllowAnyOrigin", p => p
        .AllowAnyOrigin()
        .AllowAnyHeader()
        .AllowAnyMethod());
});

builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

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

app.UseHttpsRedirection();

app.UseAuthentication();

app.UseAuthorization();

app.MapControllers();

app.UseCors("AllowAnyOrigin");


app.MapGet("/sse_appsched", async (HttpContext ctx, ItemService service, CancellationToken ct) =>
{
    ctx.Response.Headers.Add("Content-Type", "text/event-stream");

    while (!ct.IsCancellationRequested)
    {
        var item = await service.WaitForNewItem();
         
        await ctx.Response.WriteAsync($"data: ");
        await JsonSerializer.SerializeAsync(ctx.Response.Body, item);
        await ctx.Response.WriteAsync($"nn");
        await ctx.Response.Body.FlushAsync();

        service.Reset();
    }
});

app.Run();

This is code of item service:

    public record Item(string Name, double Price);
public class ItemService
{
    private TaskCompletionSource<Item?> _tcs = new();
    private long _id = 0;

    public void Reset()
    {
        _tcs = new TaskCompletionSource<Item?>();
    }

    public void NotifyNewItemAvailable()
    {
        _tcs.TrySetResult(new Item($"New Item {_id++}", Random.Shared.Next(0, 500)));
    }

    public Task<Item?> WaitForNewItem()
    {
        // Simulate some delay in Item arrival
        Task.Run(async () =>
        {
            await Task.Delay(TimeSpan.FromSeconds(Random.Shared.Next(0, 29)));
            NotifyNewItemAvailable();
        });

        return _tcs.Task;
    }
}

And this is code in WPF App:

public partial class OJISSE
{
    String UriOfEvent = "https://localhost:44329/sse_appsched";
    public async Task ServiceWrapperAsync()
    {
        using (var client = new HttpClient())
        {
            using (var stream = await client.GetStreamAsync(UriOfEvent))
            {
                using (var reader = new StreamReader(stream))
                {
                    while (true)
                    {
                        var data = reader.ReadLine();
                        Trace.WriteLine(data);
                    }
                }
            }
        }
    }

}

OJISSE OJI_SSE_INST = new OJISSE();

Task OJI_SSE_TASK = Task.Run(OJI_SSE_INST.ServiceWrapperAsync);