如何等到的await /異步方法完成

Question

我有以下的異步方法：

private async void ProcessSearch() 
{ 
    // get catalogs on first search 
    if (_invoiceTypes == null && _invoiceAccounts == null) 
    { 
     var confWcf = new Data.ConfigurationWCF(); 
     _invoiceTypes = await confWcf.GetInvoiceTypesAsync(MainForm.State.Entity); 
     _invoiceAccounts = await confWcf.GetInvoiceAccountsAsync(MainForm.State.Entity); 
     confWcf.Dispose(); 
    } 

    var seekWcf = new DataSeekWCF(); 
    _ds = await seekWcf.SearchInvoiceAdminAsync(new Guid(cboEmployer.Value.ToString()), new Guid(cboGroup.Value.ToString()), txtSearchInvoiceNumber.Text, chkSearchLike.Checked, txtSearchFolio.Text, Convert.ToInt32(txtYear.Value)); 
    seekWcf.Dispose(); 

    if (_ds != null) 
    { 
     SetupInvoiceGrid(); 
    } 
} 

我不想執行SetupInvoiceGrid直到_invoiceTypes，_invoiceAccounts和_ds已經完成。

任何線索？我做對了嗎？我應該使用任務而不是等待？

---

我想出了這個代碼，似乎是工作，看起來好像沒什麼問題，但真的不知道，如果它的正確：

private void btnSearch_Click(object sender, EventArgs e) 
{ 
    lock (lockObj) 
    { 
     if (_isBusy) 
      return; 
     else 
      _isBusy = true; 
    } 

    ShowPleaseWait(Translate("Searching data. Please wait...")); 
     if (_invoiceTypes == null && _invoiceAccounts == null) 
     { 
      var t = GetCatalogs(); 
      t.ContinueWith(t2 => 
      { 
       if (t.IsCompleted) ProcessSearch(); 
      }); 
     } 
     else 
     { 
      ProcessSearch(); 
     } 
} 

private async Task GetCatalogs() 
{ 
    // get catalogs on first search 
    Data.ConfigurationWCF confWcf = new Data.ConfigurationWCF(); 
    var task1 = confWcf.GetInvoiceTypesAsync(1); 
    var task2 = confWcf.GetInvoiceAccountsAsync(1); 
    confWcf.Dispose(); 

    await Task.WhenAll(task1, task2); 

    _invoiceTypes = task1.Result; 
    _invoiceAccounts = task2.Result; 

    if (_invoiceTypes != null) 
    { 
     cboInvoiceType.DataSource = _invoiceTypes.Tables["invoice_types"]; 
     cboInvoiceType.DisplayMember = "description"; 
     cboInvoiceType.ValueMember = "code"; 
    } 

} 

private async void ProcessSearch() 
{ 
    var seekWcf = new Data.SeekWCF(); 
    _ds = await seekWcf.SearchInvoiceAdminAsync(new Guid(cboEmployer.Value.ToString()), new Guid(cboGroup.Value.ToString()), txtSearchInvoiceNumber.Text, chkSearchLike.Checked, txtSearchFolio.Text, Convert.ToInt32(txtYear.Value)); 
    seekWcf.Dispose(); 

    if (_ds != null) 
    { 
     SetupInvoiceGrid(); 
    } 
    HidePleaseWait(); 
} 

Answer 1

我回答關於如何原來的問號（？）處理ProcessSearchAsync本身here的完成。

要並行運行任務（如註釋中所述），這裏是您的代碼修改，由於invoiceTypes == null和_invoiceAccounts == null檢查，它會變得有點複雜。注意檢查以下實現方式略有改變邏輯（之前它並WCF調用僅當_invoiceTypes和_invoiceAccounts都爲空的 - 如果只有其中一個爲空）：

private async Task ProcessSearchAsync() 
{ 

    Data.ConfigurationWCF confWcf = new Data.ConfigurationWCF(); 
    Task</*typeof _invoiceTypes*/> t1; 
    Task</*typeof _invoiceAccounts*/> t2; 

    if (_invoiceTypes == null) 
     t1 = confWcf.GetInvoiceTypesAsync(MainForm.State.Entity); 
    else 
    { 
     var tsc1 = new TaskCompletionSource</*typeof _invoiceTypes*/>(); 
     t1 = tsc1.Task; 
     tsc1.SetResult(_invoiceTypes); 
    } 

    if (_invoiceAccounts == null) 
     t2 = confWcf.GetInvoiceAccountsAsync(MainForm.State.Entity); 
    else 
    { 
     var tsc2 = new TaskCompletionSource</*typeof _invoiceAccounts*/>(); 
     t2 = tsc2.Task; 
     tsc2.SetResult(_invoiceAccounts); 
    } 


    DataSeekWCF seekWcf = new DataSeekWCF(); 
    Task</*typeof _ds*/> t3 = seekWcf.SearchInvoiceAdminAsync(new Guid(cboEmployer.Value.ToString()), new Guid(cboGroup.Value.ToString()), txtSearchInvoiceNumber.Text, chkSearchLike.Checked, txtSearchFolio.Text, Convert.ToInt32(txtYear.Value)); 

    await Task.WhenAll(new Task[] {t1, t2, t3}); 
    _invoiceTypes = t1.Result; 
    _invoiceAccounts = t2.Result; 
    ds = t3.Result; 

    if (_ds != null) 
    { 
     SetupInvoiceGrid(); 
    } 

    confWcf.Dispose(); 
    seekWcf.Dispose(); 
} 

Answer 2

到你的微小變化到了那裏會做你想做的。你可以開始新的任務，然後做其他的事情，然後在你繼續之前等待。正如@Noseratio有幫助地指出的那樣，下面的代碼片段不是生產就緒的，因爲我沒有檢查錯誤條件（如null引用等）。關鍵是你可以簡單而優雅地並行執行這些事情，而不必訴諸於使用非常多的任務API。我值得指出的一個調整是，您想要將呼叫轉移到Dispose進入延續（即，在所有await之後），因爲如果您在調用* Async方法後立即嘗試呼叫Dispose，那麼您很有可能會失敗你的WCF客戶端獲得響應的一半，awaits可能會引發拋出異常（我不感興趣）。

private async void ProcessSearchAsync() 
{ 

    Data.ConfigurationWCF confWcf = new Data.ConfigurationWCF(); 
    Task</*typeof _invoiceTypes*/> t1; 
    Task</*typeof _invoiceAccounts*/> t2; 

    // get catalogs on first search 
    if (_invoiceTypes == null && _invoiceAccounts == null) 
    { 
     t1 = confWcf.GetInvoiceTypesAsync(MainForm.State.Entity); 
     t2 = confWcf.GetInvoiceAccountsAsync(MainForm.State.Entity); 
    } 

    DataSeekWCF seekWcf = new DataSeekWCF(); 
    Task</*typeof _ds*/> t3 = seekWcf.SearchInvoiceAdminAsync(new Guid(cboEmployer.Value.ToString()), new Guid(cboGroup.Value.ToString()), txtSearchInvoiceNumber.Text, chkSearchLike.Checked, txtSearchFolio.Text, Convert.ToInt32(txtYear.Value)); 

    _invoiceTypes = await t1; 
    _invoiceAccounts = await t2; 
    _ds = await t3; 

    if (_ds != null) 
    { 
     SetupInvoiceGrid(); 
    } 

    confWcf.Dispose(); 
    seekWcf.Dispose(); 
}