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UWP - Update listview source dynamic from code behind

I have a group item. Then, each group in group item, i put it into a listview
var Groups = query.GroupBy(query => query.Name);
foreach (var group in Groups)
{
if (group.records.Count() > 2)
{
ListView listview = new ListView();
var itemsource = new ObservableCollection<FileProperties>();
var header = "";
foreach (var item in group.records)
{
header = item.Name;
itemsource.Add(new FileProperties(item.Name, item.Size, item.DateModified, item.Hash, item.Path, item.IsOrigin));
}
listview.ItemsSource = itemsource;
var itemsTemplate = (DataTemplate)this.Resources["Show"];
listview.ItemTemplate = itemsTemplate;
//test is mother listview
test.Items.Add(listview);
}
}
Now, i have a question, how can i update listview UI if i change value in group items without reset mother listview

The default ListView can be grouped by using CollectionViewSource. There is no need to create a child ListView for each group of the parent ListView.
My answer here shows how to create a grouped ListView, you may take a look. Or there are a bunch of demos on internet, you can googling them.
But the most important point here is that by using the default grouped ListView, we can simply create one data collection for the whole ListView, modify the items source collection to update the grouped children automatically, we don't need to create ObservableCollections for each group any more.

How to retrieve selected values for selected items in a ListBox?

I'm populating a ListBox in a WinForms application, this way:
listBoxUsers.DataSource = ctx.Users.ToList();
listBoxUsers.DisplayMember = "Name";
listBoxUsers.ValueMember = "Id";
how to retrieve the selected Ids when I'm setting the SelectionMode to MultiSimple
I want to do a foreach loop on them, like this:
foreach(var itemId in listBoxUsers.SelectedValues)//unfortunately not exist
{
int id = int.Parse(itemId);
// . . .
}

Since you know the type of items, you can use such code:
var selectedValues = listBox1.SelectedItems.Cast<User>().Select(x=>x.Id).ToList();
Side Note: The ListBox control lacks a GetItemValue method. A method which should work like GetItemText, but for getting values. In the linked post I shared an extension method to get the value from an item. Using that extension method you can get selected values independent from type of items:
var selectedValues = listBox1.SelectedItems.Cast<object>()
.Select(x => listBox1.GetItemValue(x)).ToList();
If for some reason you are interested to have a text representation for selected values:
var txt = string.Join(",", selectedValues);

Have you tried with the SelectedItems property?
foreach (var item in listBoxUsers.SelectedItems)
{
}

try this:
foreach (DataRowView item in listBoxUsers.SelectedItems)
{
int id=int.parse(item[0].ToString());
}

ListBox multiple Selection get all selected values

I'm having a problem since a while now an just can't find any solution that works for me. I have a ListBox which is filled up with a DataTable like
listbox.DataSource = table;
listbox.Displaymember = "Name";
listbox.ValueMember = "ID";
If I now select an item in my listbox I can get it out like:
listbox.SelectedValue.toString();
My Problem:
What can I do if I would like to have ALL selected Values from a ListBox where multiple selection is enabled and save them all in an array or something like that?!
I can't use SelectedItems cause that is not giving me the information I need.

Try this:
var lst = listBox1.SelectedItems.Cast<DataRowView>();
foreach (var item in lst)
{
MessageBox.Show(item.Row[0].ToString());// Or Row[1]...
}

Or if you want only iterate over the selected items you can use SelectedIndices property:
foreach (int i in listbox.SelectedIndices)
{
// listbox.Items[i].ToString() ...
}
Or:
foreach (var item in listbox.SelectedItems)
{
MessageBox.Show(item.ToString());
}

Cannot retrieve multiple values from a listbox c#

I am populating a listBox at runtime from a database as follows:
List<FILE_REPORT_TYPES> ReportTypes = GetReportTypesFromDatabase(ReportMappingIds)
BindingList<FILE_REPORT_TYPES> pbReportTypesBindingList = new BindingList<FILE_REPORT_TYPES>(ReportTypes);
listBoxReports.DataSource = ReportTypesBindingList;
listBoxReports.DisplayMember = "REPORT_DESCRIPTION";
listBoxReports.ValueMember = "REPORT_ID";
I then would like select multiple items on the listBox when running the windows form and retrieve each individual Value of my selections. If only one selection is made one could do the following:
listBoxReports.SelectedValue;
I would like to do the following:
var list = listBoxReports.SelectedValues;
However this is not allowed i.e. "SelectedValues" does not exist.
Some people are erroneously suggesting that in this particular case SelectedIndices may be used. It cannot be used, I am trying to retrieve the "VALUE". This cannot be done (in this particular case):
listBox.Items[i].Value;
I think the solution should be along the lines of:
foreach(var line in listBox.Items)
{
var res= ((SOME CASTING)line).Value;
}

To get the selected items you have 2 options
a.) ListBox.SelectedIndices which returns the indices of the selected items which you then need to use to look up in the Items property what the value is or
b.) ListBox.SelectedItems which returns you a collection with the selected items themselves (be aware that it is an objectlist so you need to transform the items into your appropriate datatype).
Edit: With the additional information the following is possible
List<FILE_REPORT_TYPES> mySelectedList = new List<FILE_REPORT_TYPES>();
foreach (Object selectedItem in ListBox.SelectedItems)
{
mySelectedList.Add( ((FILE_REPORT_TYPES)selectedItem) );
}

You can use ListBox.SelectedIndices or ListBox.SelectedItems.
If you want to get all selected-items, you can let the foreach cast:
foreach(FILE_REPORT_TYPES frt in listBox.SelectedItems)
{
// ...
}
or if you want to get the ReportID into a list with the help of LINQ:
List<decimal> reportIds = listBox.SelectedItems.Cast<FILE_REPORT_TYPES>()
.Select(frt => frt.REPORT_ID)
.ToList();

Alternative to the selected value you could do the following
listBoxReports.SelectedItems;

Answer (the casting is the trick):
List<decimal> reportIds = new List<decimal>();
foreach(var line in listBoxReports.SelectedItems)
{
reportIds.Add(((PB_FILE_REPORT_TYPES)line).REPORT_ID);
}

You may try like below
List<FILE_REPORT_TYPES> reportList = new List<FILE_REPORT_TYPES>();
foreach(var item in listBox.SelectedItems)
{
reportList.Add((FILE_REPORT_TYPES)item);
}

How to add item from ListView to string?

Im trying to get all the items from a listview into a string like so:
foreach(ListViewItem item in ListView1.Items)
{
thisstring += item...?
}
item.Text is not a property of item...can seem to figure this out. Any suggestions?

You could use LINQ to select all items' Text.
var allItems = ListView1.Items.Cast<ListItem>().Select(i => i.Text);
var allItemText = String.Join(",", allItems);
Note that you need to add the System.LINQ namespace.
Edit: I've read ListBox, a ListView does not have a Text property and i'm not sure what text you actually want to concat.

foreach(ListViewItem item in ListView1.Items)
{
thisstring += item.Text+",";
}
thisstring.TrimEnd(',');
isn't it that simple.

StringBuilder sb = new StringBuilder();
foreach(ListViewItem item in ListView1.Items)
{
sb.Append(item.Text);
sb.Append(',');
}
Console.WriteLine(sb.ToString().TrimEnd(','));
EDIT: As Tim and Guest said, there is not Text property for ListViewItem in ASP.Net, Windows Forms has ListViewItem and it has the text property. ASP.Net ListView does not have Text property

string.Join(" ", ListView1.Items.Cast<ListItem>().Select(i => i.Text).ToArray());