///first I have crated Popular class for storing values
public class Popular
{
public string trk_mnetid,trk_title , art_mnetid, art_name, image_url;
}
/// create popularplaylist class
public partial class PopularPlaylist : PhoneApplicationPage
{
Popular popobj = new Popular();
List<Popular> pop = new List<Popular>();
/* call json parsing it and show only "titles" in List form when i m click on perticular title i need to show details in next screen which i paser and store in popular popularplaylist class.
i use navigationservice call new screen
*/
NavigationService.Navigate(new Uri("/Popular_Module/PopularPlaylist.xaml", System.UriKind.Relative));
}
// plz tell me how to get list data in next screen
Use querystring.
Passing Value: In MainPage.xaml.cs add the following
The easiest way to pass a parameter is just to use a string, something like:
private void btnNavigate_Click(object sender, RoutedEventArgs e)
{
string url=String.Format("/Page1.xaml?parameter={0}",popular);
NavigationService.Navigate(new Uri(url, UriKind.Relative));
}
Getting Value: In Page.xaml.cs add the following
Note: It is important to override the OnNavigatedTo and after that you can use the NavigationContext to get the passed parameter.
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedTo(e);
List<string> parameterValue = NavigationContext.QueryString["parameter"];
}
Another popular syntax to get the value of the parameter is:
List<string> parameter = string.Empty;
if (NavigationContext.QueryString.TryGetValue("parameter", out parameter))
{
//do something with the parameter
}
Related
I have some property which I am using from Page2 in HomePageViewModel, When I navigate to Page2 I have changed that property and on coming back by doing NavigiationPop.
HomePage is not re-loaded/ refreshed at all as I have set the BindingContext in the constructor of HomePage, which is loaded only once.
The solution which is working for me is
Setting the BindingContext to the ViewModel on "onAppearing()", usually its not consider the best practice. But I also need to refresh the values which I have changed on Page2.
Looking forward for your valuable inputs and suggestions.
Also Pros/Cons of Setting the BindingContext in OnAppearing.
Thanks,
Hemant
It depends on you, they all can achieve the effect.
However if you want to reduce the CPU consumption of the program, then don't use the onAppearing method too much to refresh the page data.
Another method is that you can change the data of the model through Delegate/Event/MessageCenter.
You can refer to this discussion to know how to use Delegate/Event/MessageCenter.
Here I will give the sample by using MessageCenter to achieve that.
For example, the TestViewModel as follows:
public class TestViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
private string pagetitle;
public string PageTitle
{
get
{
return pagetitle;
}
set
{
if (pagetitle != value)
{
pagetitle = value;
NotifyPropertyChanged();
}
}
}
}
Then bind it in FirstPage as follows, and Subscribe MessageCenter inside it:
TestViewModel testViewModel = new TestViewModel();
BindingContext = testViewModel;
MessagingCenter.Subscribe<object>(this, "Hi", (sender) =>
{
// Do something whenever the "Hi" message is received
testViewModel.PageTitle = "Modified Title";
});
Then in the SecondPage, when changing the data by sending message. When back to FirstPage, the View Will be updated.
private void Button_Clicked(object sender, EventArgs e)
{
MessagingCenter.Send<object>(this, "Hi");
}
I have to implement autofill service for iOS in Xamarin forms, Is there any sample code ? How we can achieve it?
You can use package dotMorten.Xamarin.Forms.AutoSuggestBox from nuget .
Usage
xaml
<AutoSuggestBox PlaceholderText="Search" WidthRequest="200"
TextChanged="AutoSuggestBox_TextChanged"
QuerySubmitted="AutoSuggestBox_QuerySubmitted"
SuggestionChosen="AutoSuggestBox_SuggestionChosen"/>
Code Behind
private void AutoSuggestBox_TextChanged(AutoSuggestBox sender, AutoSuggestBoxTextChangedEventArgs args)
{
// Only get results when it was a user typing,
// otherwise assume the value got filled in by TextMemberPath
// or the handler for SuggestionChosen.
if (args.Reason == AutoSuggestionBoxTextChangeReason.UserInput)
{
//Set the ItemsSource to be your filtered dataset
//sender.ItemsSource = dataset;
}
}
private void AutoSuggestBox_SuggestionChosen(AutoSuggestBox sender, AutoSuggestBoxSuggestionChosenEventArgs args)
{
// Set sender.Text. You can use args.SelectedItem to build your text string.
}
private void AutoSuggestBox_QuerySubmitted(AutoSuggestBox sender, AutoSuggestBoxQuerySubmittedEventArgs args)
{
if (args.ChosenSuggestion != null)
{
// User selected an item from the suggestion list, take an action on it here.
}
else
{
// User hit Enter from the search box. Use args.QueryText to determine what to do.
}
}
For more details you can check https://github.com/dotMorten/XamarinFormsControls/tree/master/AutoSuggestBox
Does Entity Framework incorrectly detect changes to images?
I have a "Person" entity class defined as follows;
public class Person
{
public int Id { get; set; }
public byte[] Photo { get; set; }
}
I have bound the Photo to a PictureBox control on my form using a datasource.
There form also uses a dynamically created bindingNavigator.
I also have written an audit log to populate captured changes
The procedure calls the ObjectContext DetectChanges() and then
var entries = ObjectContext.ObjectStateManager.GetObjectStateEntries()
Which contains an entry showing that the Photo has been modified.
entry.OriginalValues[name] matches entry.CurrentValues[name]
The Column is varbinary(MAX) in SQL Server and the size of the picture files I have loaded are under 1Mb
If I set all of the columns to null the error no longer occurs
The code I use to get the file is
private void LoadPhotoButton_Click(object sender, EventArgs e)
{
using (var dlg = new OpenFileDialog())
{
dlg.Filter = "JPEG files |*.jpg";
if (dlg.ShowDialog() == DialogResult.OK)
{
PhotoPictureBox.Image = Image.FromFile(dlg.FileName);
}
}
}
I note here that hex zero can be inserted as padding characters when these fields are involved in string conversion.... could the binding be doing that somehow?
If I delete the picturebox from the form, or even bind the control as a text box instead of a picturebox then the behaviour is correct ( not that a picture bound to a text box is any use )
I am able to work around the problem by not binding directly to the picture box.
Instead I just load it on the BindingSource_CurrentChanged event using
private void BindingSource_CurrentChanged(object sender, EventArgs e)
{
var obj = (Person) BindingSource.Current;
this.PictureBox.Image = byteArrayToImage( obj.Photo);
}
public Image byteArrayToImage(byte[] byteArrayIn)
{
MemoryStream ms = new MemoryStream(byteArrayIn);
Image returnImage = Image.FromStream(ms);
return returnImage;
}
I am using my work around - documented at the end of the question as a make do answer.
All of my tables have common audit fields: modifiedBy,modifiedDateTime, etc.
I would like to have these automatically set, and can set most of them with the following code:
partial class myEntities
{
partial void OnContextCreated()
{
this.SavingChanges += new EventHandler(Entities_SavingChanges);
}
private void Entities_SavingChanges(object sender, EventArgs e)
{
IEnumerable<ObjectStateEntry> objectStateEntries =
from ose
in this.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified)
where ose.Entity != null
select ose;
var auditDate = DateTime.Now;
var auditUser = System.Web.HttpContext.Current.User.Identity.Name;//I wish
foreach (ObjectStateEntry entry in objectStateEntries)
{
ReadOnlyCollection<FieldMetadata> fieldsMetaData = entry.CurrentValues.DataRecordInfo.FieldMetadata;
FieldMetadata modifiedField = fieldsMetaData.Where(f => f.FieldType.Name == "ModifiedBy").FirstOrDefault();
if (modifiedField.FieldType != null)
{
string fieldTypeName = modifiedField.FieldType.TypeUsage.EdmType.Name;
if (fieldTypeName == PrimitiveTypeKind.String.ToString())
{
entry.CurrentValues.SetString(modifiedField.Ordinal, auditUser);
}
}
}
}
}
The problem is that there doesn't appear to be any way to get access to the current user. The app is intranet only, using Windows auth.
Is there a way to either pass in a parameter, or get access to the HttpContext (which doesn't seem like it would be a good idea, but I'm stuck)? Is there a way to populate the EventArgs with information?
Check out the section where the poster has overridden the SaveChanges method (6th code box down on the page). This way you can pass in the UserID and perform your audit and not have to use an event handler.
I have a simple user control in Windows Phone 7 and I want to get access to the querystring collection from the user controls Constructor. I have tried many ways and cannot seem to get acess to the containing XAML's querystring collection.
Essentially I am navigating to the page and the my user control is going to access the querystring value to write the value back to the interface.
Am I missing adding an assembly or reference or something?
I am not sure you should be trying to get at the information from the page's constructor, as it won't necessairly get called every time you land on this page. A better approach is to override the OnNavigatedTo method inherited from PhoneApplicationPage. Looking a little more carefully at your question, you may be trying to do this within a control embedded in the page, in which case you need to get at the Page in order to obtain the navigation information.
Regardless, the NavigationContext property from the page has a QueryString parameter that you can use to access the information you're after.
The following example assumes I have a parameter named "Message" in the query string when navigating to this page:
public partial class MyPage : PhoneApplicationPage
{
// Constructor
public MyPage()
{
InitializeComponent();
}
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedTo(e);
String navigationMessage;
if (NavigationContext.QueryString.TryGetValue("Message", out navigationMessage))
{
this.textBlock1.Text = navigationMessage;
}
}
}
Sorry about that - I started to get there, and thanks for the clarification. Your best bet then is to walk up the visual tree from your control to find the Page, then you can have at the NavigationContext. In my sample below, I have a button on a custom control within the page, whose click event finds the nav context and looks for a certain navigation parameter - I couldn't tell from the question or your follow-up what would drive the control to "want" to find the content of the query string.
(Note about getting info from the ctor follows the code below)
public partial class WindowsPhoneControl1 : UserControl
{
public WindowsPhoneControl1()
{
InitializeComponent();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
GetTheQueryString();
}
private void GetTheQueryString()
{
var result = "No Joy";
var page = FindRootPage(this);
if (page != null)
{
if (page.NavigationContext.QueryString.ContainsKey("Param"))
{
result = page.NavigationContext.QueryString["Param"];
}
}
queryStringText.Text = result;
}
private static PhoneApplicationPage FindRootPage(FrameworkElement item)
{
if (item != null && !(item is PhoneApplicationPage))
{
item = FindRootPage(item.Parent as FrameworkElement);
}
return item as PhoneApplicationPage;
}
}
Note that this won't work from the ctor because of how Xaml works...the Xml tag drives the ctor to be called, then properties are set as indicated, then it is added as a child/item/etc in its container. If you do need to get at the context ASAP using this "walk up the tree" technique, handle the Control's Loaded event, by which time the control does have a parent and a tree that can be walked...
public WindowsPhoneControl1()
{
InitializeComponent();
Loaded += WindowsPhoneControl1_Loaded;
}
private void WindowsPhoneControl1_Loaded(Object sender, RoutedEventArgs e)
{
GetTheQueryString();
}
I would add a property to the UserControl subclass that would be set by the page in its OnNavigatedTo() method.