Develop Reference

ScrollViewer has line across at topmost and bottommost positions

I have a ScrollViewer, which contains a set of items in a WrapPanel. The xaml tree is as follows:
<Grid>
<ScrollViewer>
<ItemsControl ItemsSource="{Binding xyz}" Tag="{Binding .}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel IsItemsHost="True" Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Button.... styling etc.>
When scrolled to the very top or very bottom position, a white line appears across the control- image is here: https://imgur.com/3DNpWRE
This is happening in a view which uses VisualStates. There are other visual states which use a ScrollViewer, and this problem does NOT happen. The only thing unique about this particular visual state is the use of the ItemsPanel/WrapPanel. I've tried removing this just to isolate the cause of the problem, and even when I take it our the issue persists.
Seems almost like the scroller fails to fully refresh/paint when it gets to the first/last index.
Has anyone seen something like this before?
Interestingly enough, if I run my application in debug, the scroller displays perfectly fine. Only when launching a release build does the problem present itself.

How to customize a ListView like this in wpf c#?

I'm new to app dev. I am now stuck in the design of my app. This item is an item like a bulletin board. Just do not know which way is the right way to design my data in this style below? I had no idea whether to use the DATAGRIDVIEW OR LISTVIEW/LISTBOX?
Hope to get some idea from you guys

As Nex said, you are better off making the design shown in your picture as a usercontrol and after you do that use a ListView with a data template like this:
<ListView x:Name="mylistview">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
//a Panel container (i.e stackpanel, wrappanel)
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemTemplate>
<DataTemplate>
//Your usercontrol
</DataTemplate>
</ListView.ItemTemplate>
and of course you will need to use data binding to show your data.

Horizontal Listview in Xamarin.Forms

As the title stated above, I want to create horizontal ListView in xamarin.forms.
But the solutions and the examples that I found are not the kind of horizontal list that I want.
Every articles that i stumbled upon, the items are arranged like this
item1____item2____item3____item4____item5
What I want to do is something like this
item1___item2
item3___item4
item5___and so on
in windows phone we can do it like this
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<toolkit:WrapPanel ItemWidth="222" ItemHeight="100"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
Right now, is it possible to create something like this in xamarin.forms?

To my knowledge there is no such thing implemented directly in Xamarin Forms. But there is a FlowListView control from Daniel Luberda. Maybe this is what you want:
https://github.com/daniel-luberda/DLToolkit.Forms.Controls/tree/master/FlowListView/

GridView SelectedItem indicator not present on Windows Phone Xaml

on Windows 8.1 below code indicates the selected item of GridView. But on Windows Phone Xaml same code doesn't work like that. There isn't any visual indicator for selected item at all.(or i couldn't get it to work) How can i make it work like this on Windows Phone App too?
<GridView
x:Name="productColorChoices"
SelectionMode="Single"
ItemTemplate="{StaticResource productColorChoice_ItemTemplate}">
<GridView.ItemsPanel>
<ItemsPanelTemplate>
<VariableSizedWrapGrid
Orientation="Horizontal" />
</ItemsPanelTemplate>
</GridView.ItemsPanel>
</GridView>

If you go look at the GridViewItem default style template you'll see towards the bottom you have these objects in there;
SelectedBorder
SelectedCheckMarkOuter
SelectedCheckMark
SelectedEarmark
Which is what makes up the visuals for that selected outline/checkmark thingy on the GridView items. They all get shown according to the VisualState for Selected
Now, if you go and look at the phone's default style template for the GridViewItem's (which I couldn't find the default one for with a quick google search and I don't have a phone project open to go dig through) then you can compare. If these types of elements don't exist in the phone templates then you can go add them the same way using pretty much the same objects and the same storyboards in the same VisualState.
Hope this helps, cheers.

ListBox horizontal scroll-to method C# WP 8.0

I'm trying to use in my application an input-selected index to scroll a ListBox (horizontally scrollable). I've found on MSDN and on this own site the method ScrollIntoView but it doesn't work and on the ListBox Class page it has been written to be compatible with WP 7.0, 7.1. So, this is a snapshot of my code...
scrolling.ScrollIntoView(scrolling.Items[20]);
where scrolling is my ListBox and the 20th item is the one I want to be selected and visualized.
PS: I've already tried to use the selectedIndex way but it is still not working!
This is a xaml of my ListBox (put in the Layout Grid) which have referencies to templates written in the App.xaml document.
<ListBox x:Name="scrolling" Grid.Column="0" ScrollViewer.ManipulationMode ="Control" ScrollViewer.VerticalScrollBarVisibility="Disabled" ScrollViewer.HorizontalScrollBarVisibility="Visible">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
edit: I found that calling the function by a button makes the all whole stuff work, but how to initialize everything at the start?

I used in my solution first updated UI and then called ScrollIntoView it works fine:
scrolling.UpdateLayout();
scrolling.ScrollIntoView(scrolling.Items[20]);