在哪里标记 lambda 表达式异步？

Question

我有这个代码：

private async void ContextMenuForGroupRightTapped(object sender, RightTappedRoutedEventArgs args)
{
    CheckBox ckbx = null;
    if (sender is CheckBox)
    {
        ckbx = sender as CheckBox;
    }
    if (null == ckbx)
    {
        return;
    }
    string groupName = ckbx.Content.ToString();

    var contextMenu = new PopupMenu();

    // Add a command to edit the current Group
    contextMenu.Commands.Add(new UICommand("Edit this Group", (contextMenuCmd) =>
    {
        Frame.Navigate(typeof(LocationGroupCreator), groupName);
    }));

    // Add a command to delete the current Group
    contextMenu.Commands.Add(new UICommand("Delete this Group", (contextMenuCmd) =>
    {
        SQLiteUtils slu = new SQLiteUtils();
        slu.DeleteGroupAsync(groupName); // this line raises Resharper's hackles, but appending await raises err msg. Where should the "async" be?
    }));

    // Show the context menu at the position the image was right-clicked
    await contextMenu.ShowAsync(args.GetPosition(this));
}

……Resharper的检查抱怨道，“因为没有等待此调用，所以在调用完成之前继续执行当前方法。请考虑将‘wait’运算符应用于调用结果”（在注释行）。

所以，我在它前面加了一个“等待”，但当然，我也需要在某个地方加一个“异步”——但在哪里呢？

Answer 1

如果您在LINQ方法语法中，请在参数前应用async关键字:

 list.Select(async x =>
            {
                await SomeMethod(x);
                return true;
            });

Answer 2

对于那些使用匿名表达式的人：

await Task.Run(async () =>
{
   SQLLiteUtils slu = new SQLiteUtils();
   await slu.DeleteGroupAsync(groupname);
});

Answer 3

要标记lambda async，只需在其参数列表前加上< code>async:

// Add a command to delete the current Group
contextMenu.Commands.Add(new UICommand("Delete this Group", async (contextMenuCmd) =>
{
    SQLiteUtils slu = new SQLiteUtils();
    await slu.DeleteGroupAsync(groupName);
}));