我在哪里标记一个lambda表达式异步?

我有这样的代码:

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，“因为没有等待此调用，所以当前方法的执行将在调用完成之前继续进行。考虑对调用结果应用'await'操作符”(在注释行)。

因此，我在它前面加上了一个“await”，但是，当然，我还需要在某个地方添加一个“async”，但是在哪里呢?

211504 次浏览

小开

最佳答案

要标记一个lambda async对象，只需在其参数列表前加上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);
}));

小开

对于那些使用匿名表达的人:

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

小开

如果你在LINQ方法语法中，在参数前应用async关键字:

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