about how xamarin.forms is displayactionsheet in the context of MVVM

I've been working on Xmarin.forms recently, and I've come across a tricky question about how to use Displayactionsheet in ViewModel in the context of MVVM, but I'm using XAML mode, which means that only in a background page can you use the page's exclusive disp Layactionsheet. Looking for an afternoon information, online said, can give each other a bridge, so that ViewModel and page connected together.

First, you need to use Messagingcenter to write a Displayactionsheet method on your page.

 Messagingcenter.subscribe<baseviewmodel, displayactionsheetmodel> (this ,  displayactionsheet   ", async  (sender, values) => string  result = String.Empty; Result  = await   Displayactionsheet (Val UEs. Title, values. Buttonone, values. Buttontwo, values.                Displayvalues);  if  (values.                    OnCompleted! = null  

Baseviewmodel this place, of course, you write the ViewModel or application you belong to.
In Baseviewmodel we need to configure the bridge so that our ViewModel can connect to the page

 Public Async Task Displayactionsheet (Displayactionsheetmodel actionsheetmodel)        {            messagingcenter.send<baseviewmodel, displayactionsheetmodel> (this"  Displayactionsheet", Actionsheetmodel);        }

Then we can use it again in ViewModel.

 varActionsheetmodel =NewDisplayactionsheetmodel (); Actionsheetmodel.title="Is you sure?"; Actionsheetmodel.buttonone="Cancel"; Actionsheetmodel.displayvalues=New string[]            {                "Yes","No","I donw ' t know","I ' m sure!","..."            }; Actionsheetmodel.oncompleted+ = (accept) = ={disdata=Accept;            }; awaitDisplayactionsheet (Actionsheetmodel);

With a construction class you can easily pass the data to the page, then the problem

We can now pass the required properties in Displayactionsheet to the page using ViewModel, so how do we get the data from the page back to ViewModel?

Presumably everyone saw the oncompleted, so you can look at my model

  Public classDisplayactionsheetmodel { Public stringTitle {Get;Set; }  Public stringButtonone {Get;Set; }  Public stringButtontwo {Get;Set; }  Public string[] Displayvalues {Get;Set; }  Publicaction<string> oncompleted {Get;Set; } }

So that after you choose it will give you the choice of things to the value of Action<string>, and then we use

OnCompleted + = (accept) =            {                disdata = accept;            };
This way, assign the value of the selection to Disdata next look

Of course, I'm clicking on the second button before it pops up my selected I ' m sure

Private Async Task distest ()        {            await DisplayAlert ("Test", Disdata);        }

So there is a problem, what if I want to do something about the selected value after I choose?

I tried a lot of ways, like Task.waitall (), and the only thing that would play a role is to await task.delay (1000); Let the next operation wait 1 seconds, if I choose fast, no problem, but if I choose the slow, still not, the symptoms do not cure, so , looked for an afternoon information also did not find the right solution, please friends, do you have a good solution?

If there is, please help the younger brother pointing to the maze, younger brother grateful ...

about how xamarin.forms is displayactionsheet in the context of MVVM