在 WPF 中使用 EntityFrameWork 加载数据时显示进度条

Question

我想在Progressbar 中显示从数据库中获取数据的进度。目前我正在更新Button 的内容。不知道如何在这段代码中实现。

private async void FetchInvoicesDataFunc(object sender, RoutedEventArgs e)
 {
   ProgressBtn.Content = "Loading Data ...";
   InvoiceGrid.ItemsSource = await  Task.Run(FetchInvoiceDataAsync);
   ProgressBtn.Content = "Loaded !";

 }

private async Task<List<Invoice>> FetchInvoiceDataAsync()
 {
   List<Invoice> result;
   using(var context = new Intelliventory_DBEntities() )
    {  
      result  = await context.Invoices.Where(b => b.InvoiceID <= 2000).Include(x => x.Customer).ToListAsync();      
    }
        return  result;
    }
}

Answer 1

您将无法显示 EF 查询的百分比，因为它不会通知您数据库查询的进度（我不知道有任何数据库系统可以让客户了解查询的状态）

您可以考虑将您的查询拆分成这样的部分：

 private async void FetchInvoicesDataFunc(object sender, RoutedEventArgs e)
 {
   List<Invoice> results = new List<Invoice>();
   ProgressBtn.Content = "Loading Data ...";
   await Task.Run(async() => results.AddRange(await FetchInvoiceDataAsync(0, 500));  
   ProgressBtn.Content = "25% done...";
   await Task.Run(async() => results.AddRange(await FetchInvoiceDataAsync(501, 1000)); 
   ProgressBtn.Content = "50% done...";
   await Task.Run(async() => results.AddRange(await FetchInvoiceDataAsync(1001, 1500)); 
   ProgressBtn.Content = "75% done...";
   await Task.Run(async() => results.AddRange(await FetchInvoiceDataAsync(1501, 2000));        
   InvoiceGrid.ItemsSource = results;
   ProgressBtn.Content = "Loaded !";    
 }

 private async Task<List<Invoice>> FetchInvoiceDataAsync(int start, int end)
 {
   List<Invoice> result;
   using(var context = new Intelliventory_DBEntities() )
   {  
     result  = await context.Invoices.Where(b => b.InvoiceID >= start && b.InvoiceID <= end).Include(x => x.Customer).ToListAsync();      
   }

   return  result;
 }

请注意，这将对您的应用程序的性能产生负面影响。 有成千上万的教程如何在 WinForms 和 WPF 中使用进度条，所以我不会深入探讨这个话题。