Vfrdtyky

In my xamarin.forms i need to load data while app start . I know that the code must be in App.cs page. I can load data on a button click, now i want to load the data while app start . what is the right solution for that

You can use async/await, if you need the download to be completed and do something with your data while you're still on the OnStart method:

protected async override void OnStart()

{

    // Handle when your app starts



    //retrieve your data

    TypeOfDataObject dataObj = await GetMyData();



   // Do stuff with your data

}



private Task<TypeOfDataObject> GetMyData()

{

      //Get your data from URL

      return dataObj;

}

You need to await the data and also make sure that you deal with not being able to get the data and give the user the chance to retry.

Here is how I've done this:

protected async override void OnStart ()

{

    do

    {

        try

        {

            _data = await GetData();

        }

        catch(Exception e)

        {

             var errorMessage = e.Message; // Todo: Use nicer error message

             await loadingPage.DisplayAlert ("Error", errorMessage, "RETRY");

        }

    } while (_data = null);



    // Do stuff with _data

}

You can see a full example of this working along with displaying a loading page in my DDD North Agenda App Sample.

Just start loading data in the constructor of your App.cs. You can do it on a background thread if needed.

Task.Run(() =>

            {

                // Do stuff in here

            });

Use a ContinueWith to handle any exceptions.

Update

As per my comments below, I don't recommend this way, using the OnStart is a much better approach.

Add an Async in there and load that way. The constructor needs to return and return with 17 seconds in the case of iOS.

protected async override void OnStart()

{



}

Also, make sure you place a try/catch around all that code because there is no Task to return an exception.