Can a BindingContext object data binding object directly be changed on changing of an entry field?

Question

I am new to xamarin, i hope someone can help me with this:

I have a sinple page with entry fields and data binding.

I have page A with a listview. When I click on an item, I get redirected to page B which has the form elements.

 async void LvData_ItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            if (e.SelectedItem != null)
            {
                var secondPage = new ProfileDataPage();
                secondPage.BindingContext = e.SelectedItem;
                await Navigation.PushAsync(secondPage);
            }
        }

This works, and in page B the fields are filled with the right data.

So now I change the value of an entry field. Then I click on the Save Button and I do something like this (profileData = BindingContext object):

 profileData.Height = Functions.ToNullableDouble(Height.Text);
profileData.Weight = Functions.ToNullableDouble(Weight.Text);
etc...

Doesn't the BindingContext know somehow that the value of the entry has changed, and I can just send the BindingContext object to my web api for save, update and so on?

Thank you very much.

You need to bind your entry text property to the profileData field you want to be updated by. I strongly advise you to check how binding works in XF and check binding modes that are available. Also, check INotifyPropertyChanged. — Umar3x, Oct 31 '19 at 00:08
as Umar3x said,you could check your model of profileData,whether it implements `INotifyPropertyChanged` ? — Leo Zhu, Oct 31 '19 at 01:47
Thx, I will look at this. Do i need INotifyPropertyChanged for every field or can I do it for the whole class at once? You have any good link for me to read into it? Thank you very much! — JYB, Oct 31 '19 at 01:52

Leo Zhu · Accepted Answer · 2019-10-31T02:53:09.570

for example,here is a mode:

class MyData : INotifyPropertyChanged
{
    string height;
    string weight;
    public MyData(string height,string weight)
    {
        this.height= height;
        this.weight= weight;
    }

    public string Height
    {
        set
        {
            if (height!= value)
            {
                height= value;
                OnPropertyChanged("Height");

            }
        }
        get
        {
            return height;
        }
    }
   public string Weight
    {
        set
        {
            if (weight!= value)
            {
                weight= value;
                OnPropertyChanged("Weight");

            }
        }
        get
        {
            return weight;
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

you could refer to Binding Mode

score 0 · Answer 2 · answered Oct 31 '19 at 14:19

0

So I tried your solutions, which helped, but only after I have update my VS, all the nuget packages and so on..

came to this idea by this post: Link

I have no idea why this was necessary, but it works now!

Thank you!

answered Oct 31 '19 at 14:19

JYB

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Can a BindingContext object data binding object directly be changed on changing of an entry field?

2 Answers2