需要使用HttpResponseStreamWriter而不是JsonWriter，以便在输出流的末尾添加换行符，并在返回的响应中正确设置文本/事件流MIME类型。

以下是一个示例：

ASP.NET Core API的控制器方法：

[HttpGet] [Produces("text/event-stream")] public async Task Get() { var response = HttpContext.Response; response.Headers.Add("Content-Type", "text/event-stream"); response.Headers.Add("Cache-Control", "no-cache");

var data = "data: Some data\n\n";
var buffer = Encoding.UTF8.GetBytes(data);

await response.Body.WriteAsync(buffer, 0, buffer.Length);
await response.Body.FlushAsync();

// Indicates end of stream
await response.Body.WriteAsync(Encoding.UTF8.GetBytes("event: end\r\n"), 0, Encoding.UTF8.GetByteCount("event: end\r\n"));

}

Angular端的服务方法应该使用EventSource进行订阅。以下是一个示例：

@Injectable({ providedIn: 'root' })

export class StreamingService { private source: EventSource; private apiUrl: string = 'https://localhost:44321/streaming/get';

subscribeToData(): Observable {
    return new Observable(observer => {
        this.source = new EventSource(this.apiUrl);

        this.source.addEventListener('error', error => {
            console.log('EventSource error: ', error);
            this.source.close();
            observer.error(error);
        });

        this.source.addEventListener('end', error => {
            console.log('EventSource closed');
            this.source.close();
            observer.complete();
        });

        this.source.onmessage = event => {
            const data = JSON.parse(event.data);
            observer.next(data);
        };
    })
}

}

这样就可以正确地使用EventSource与ASP.NET Core API中的数据流进行通信了。