c# – Windows窗体卡在多个异步任务上

请纠正我做错了什么.这是代码：

public partial class Form1 : Form
{
   private async void button1_Click(object sender,EventArgs e)
   {
      var itemList = new List<string>() { "Field1","Field2","Field3" };

      await Task.WhenAll(itemList.Select(item =>
           new WorkToDo(item).StartWork()
           ));
    }
}

public class WorkToDo
{
    private string id;

    public WorkToDo(string id)
    {
        this.id = id;
    }

    public async Task<bool> StartWork()
    {
        Calculate();
        Analyze();
        SomeToDo();
        var result = Save();
        await Task.Delay(100);
        return result;
    }

    private bool Calculate()
    {
        //Some complex and time taking calculation will be here
        return true;
    }

    private bool Analyze()
    {
        //Some complex and time taking calculation will be here
        return true;
    }

    private bool SomeToDo()
    {
        //Some complex and time taking calculation will be here
        return true;
    }

    private bool Save()
    {
        //Some complex and time taking calculation will be here
        return true;
    }
}