如何等待等待/async方法完成

本文关键字：等待 async 方法 何等待 | 更新日期: 2023-09-27 18:27:59

我有以下异步方法：

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();
    }
}

在_invoiceTypes、_invoiceAccounts和_ds完成之前，我不想执行SetupInvoiceGrid。

有线索吗？我做得对吗？我应该使用Task而不是等待吗？

我已经想出了这个代码，它似乎正在工作，对我来说看起来很好，但不知道它是否正确：

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();
}

如何等待等待/async方法完成

我在这里回答了关于如何处理ProcessSearchAsync本身的完成的原始（？）问题。

要并行运行任务（如注释中所述），以下是您修改的代码，由于invoiceTypes == null和_invoiceAccounts == null检查，它变得有点复杂。请注意，下面的检查实现方式稍微改变了逻辑（以前它只在_invoiceTypes和_invoiceAccounts都为null的情况下进行WCF调用——如果其中只有一个为null怎么办？）：

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();
}

对现有内容的微小更改将满足您的需求。你可以开始新任务，然后做其他事情，然后在继续之前等待。正如@Noseratio所指出的，下面的这个片段还没有准备好生产，因为我没有检查错误条件（如null引用等）。重点是，您可以简洁而优雅地并行完成这些工作，而不必使用大量的Tasks API。我做的一个值得指出的调整是，您希望将对Dispose的调用转移到continuation中（即，在所有await之后），因为如果您在调用*Async方法之后立即尝试Dispose，则很有可能在获得响应的中途杀死WCF客户端，并且awaits可能最终会抛出异常（我没有发现）。

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();
}
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