如何使用同一方法多次刷新父组件中的子组件？

Question

Right now my child component only updates once the GetLeads() method in the parent component is finished. I never see the spinner or Searching text.

Parent Component:

<SearchResultComponent  @ref="ChildComponent"></SearchResultComponent>

Code:

 protected SearchResultComponent ChildComponent;
 public int LeadsFound { get; set; }
 public void GetLeads()
 {
      ChildComponent.Refresh(true, 0);
      var leads  = _searchService.Search(searchRequest);
      LeadsFound = leads?.Count ?? 0;
      _writeFileService.WriteToFile(leads);
      ChildComponent.Refresh(false, LeadsFound);
  }

Child Component:

@code {

    public bool Searching { get; set; } = false;
    public int LeadsFound { get; set; } = 0;
    public void Refresh(bool searching, int leadsFound)
    {
        Searching = searching;
        LeadsFound = leadsFound;
        StateHasChanged();
    }
}

@if (Searching)
{
    <div>Searching...</div>
    <div>
        <img src="~/Content/searching-spinner.gif" />
    </div>
}
else
{
    <div>Leads Found: @LeadsFound</div>
}

Answer 1

my child component only updates once

You can make the eventhandler async. That allows you then to call Task.Delay(1) or Task.Yield() and that will effectuate the StateHasChanged().

The call form @onclick="@GetLeads" can remain the same. Note that you don't need the 2nd @ in there.

If your searchService.Search() was async then you wouldn't need Task.Yield()

 public async Task GetLeads()
 {
      ChildComponent.Refresh(true, 0);      
      await Task.Yield();  // enable the render thread to run.
      var leads  = _searchService.Search(searchRequest);
      LeadsFound = leads?.Count ?? 0;
      _writeFileService.WriteToFile(leads);
      ChildComponent.Refresh(false, LeadsFound);
  }