我的 Blazor 服务器端应用程序的范围服务正在从远程 PC 循环读取过程值。如何在我的剃须刀页面上实时显示此值？

Question

在我的 Blazor 服务器端应用程序中，我有一个范围服务，它正在从远程 PLC 循环读取过程值。通过下面的代码，我尝试在我的剃刀页面上实时显示该值。但只显示一个值（未实现，尽管该值是动态变化的）。数据似乎没有从服务正确传输到剃刀页面。可能是什么问题：

我的范围服务代码：(Data_reader_service)

   public void read_data_cyclic()
   {
      try
      {         
      
      for(int y=0; y<10; y++)
      {
        //here I am reading process value from a remote PLC cyclic to the var. item_value. I can verify that the values are read by writing to a log file.
        using (StreamWriter sw2 = File.AppendText(log_path))
        {
          sw2.WriteLine("val-"+y+":"+item_value+" "+Convert.ToString(DateTime.Now));
        }                                           
        // here I pass the values to the event handler             
        Pass_item(item_value);            
        Thread.Sleep(1000);
        // next cycle data reading
      }
      catch
      {
          //Error handling;
      }
    }

    public string Pass_item(string new_item)
    {            
        Item_Changed?.Invoke(Item_Changed, new_item);
        return new_item;
    }

    public event EventHandler<string> Item_Changed;

我的剃刀页面的代码（当我单击按钮时，服务将开始读取数据）

   @inject Data_reader_service Data_reader_service
   <table>
   <tr>        
      <td>
        <button @onclick="call_read_data_service">
        </button>
      </td>
      <td>@item_value</td>
   </tr>
   </table>

我的razor页面的cs代码：

    public async Task call_read_data_service()
    { 
      await Task.Run(() => Data_reader_service.read_data_cyclic());
      //this time I have set for to be sure that the service has connected to remote PLC and started to read data
      Thread.Sleep(5000);
      Data_reader_service.Item_Changed += Item_Changed;
    }

    string item_value;
    private async void Item_Changed(object sender, string new_item)
    {
        await InvokeAsync(() =>
        {
            // Set the local counter variable
            item_value = new_item;
            // Tell Blazor to rewrite the DOM
            StateHasChanged();
        });
    }  

Answer 1

我注意到我只检查了一次 razor.cs 代码中的值更改。 我更改了我的 razor.cs 代码，如下所示，它起作用了：

// I added a Timer
public System.Timers.Timer timer1 = new System.Timers.Timer();

public async Task call_read_data_service()
{ 

  timer1.Elapsed += new ElapsedEventHandler(OnTimedEvent1);
  timer1.Interval = 1000;
  timer1.Enabled = true;

  await Task.Run(() => Data_reader_service.read_data_cyclic());  
}

// Checked the Item_Changed event every second
public void OnTimedEvent1(object source, ElapsedEventArgs e)
{
    Data_reader_service.Item_Changed += Item_Changed;
}

string item_value;
private async void Item_Changed(object sender, string new_item)
{
    await InvokeAsync(() =>
    {
        // Set the local counter variable
        item_value = new_item;
        // Tell Blazor to rewrite the DOM
        StateHasChanged();
    });
}