Hello,

first of all, thank you for relelasing Dialog, it is what we are "simulating" by modal Window on any kind of heavy data editing app,again and again and again :) .

The problem is,
- when you put DropDownList in Dialog, using OnRead async task event, the UI is still "empty". => Iam fiddled with reassigning datasource, changing order of assigning source, nothing helped.
- same dropdownlist scenario inside window, working/displayed as expected.

Steps to reproduce:
1) click on then button to show window by -> async task
2) event OnRead of the dropdownlist is correctly called, data to the IEnumerable<model> is loaded
3) window appear, but DropDownList is empty
4) when you filter by typeing inside DropDownList, OnRead is called and model populated, but GUI is still empty

What doesnt worked:
- statechaned, reassign datasource, clear datasource, task delay

What partially worked:
- OnRead=> async Task changed to just: OnRead=> Task

Thanks for info what should be made done else.

Stripped sample:
<TelerikButton @onclick="@(() => ParamEd(4444, null))">open window or dialog</TelerikButton>
<TelerikWindow Modal="true" @bind-Visible="@ShowEditWindow" Draggable="true">
<WindowTitle>
<strong>@ShowEditWindowCaption</strong>
</WindowTitle>
<WindowContent>

<TelerikDropDownList @bind-Value="@CurrentEdit.ValTxt"
ScrollMode="@DropDownScrollMode.Virtual"
Data="@CurrentEdit.ComboSource"
OnRead="@ReadComboData"
ItemHeight="30"
TotalCount="@Paging.CNT"
PageSize="14"
PopupHeight="400px"
TextField="Nazev1"
ValueField="KeyVal"
Filterable="true"
FilterOperator="StringFilterOperator.Contains">
</TelerikDropDownList>
....
vs
<TelerikDialog @bind -Visible="@ShowEditWindow" Title="@ShowEditWindowCaption" CloseOnOverlayClick="false">
<DialogContent>
<TelerikDropDownList @bind-Value="@CurrentEdit.ValTxt"
ScrollMode="@DropDownScrollMode.Virtual"
Data="@CurrentEdit.ComboSource"
OnRead="@ReadComboData"
ItemHeight="30"
TotalCount="@Paging.CNT"
PageSize="14"
PopupHeight="400px"
TextField="Nazev1"
ValueField="KeyVal"
Filterable="true"
FilterOperator="StringFilterOperator.Contains">
</TelerikDropDownList>
....
@code{

//clicked on the button to show window/dialog:
async Task ParamEd(int xtyp, object it)
{
await Task.Delay(500);//await load captions... and THEN open window:
ShowEditWindowCaption = "window title";
ShowEditWindow = true;
}

async Task ReadComboData(DropDownListReadEventArgs e)
{
try
{
var r = await readDBDATA...
//CurrentEdit.ComboSource = new List<EdBase>();
//CurrentEdit.ComboSource = null;
//CurrentEdit.ComboSource = new IEnumerable<EdBase>(r);
//CurrentEdit.ComboSource = await ReadDBDATA
CurrentEdit.ComboSource = r;
Paging.CNT = p.Get<int>("CNT");

/*
//!! HOTFIX FROM ANOTHER BUG(show selected data) - ReAssign data(but id doesnt impact result):
string v = CurrentEdit.ValTxt;
int? i= CurrentEdit.ValInt;
CurrentEdit.ValTxt = string.Empty;
CurrentEdit.ValInt = null;
StateHasChanged();
//await InvokeAsync(() => StateHasChanged());
CurrentEdit.ValTxt = v;
CurrentEdit.ValInt = i;

//CurrentEdit.ValTxt = CurrentEdit.ValTxt;
//StateHasChanged();
*/
}
catch (Exception ex)
{
Notification.ShowSQLErr(ex.Message);
}
}

//PARTIALLY WORKING, but not filtering:
Task ReadComboData(DropDownListReadEventArgs e)
{
try
{
var r = readDBDATA...
CurrentEdit.ComboSource = r;
Paging.CNT = p.Get<int>("CNT");
}
catch (Exception ex)
{
Notification.ShowSQLErr(ex.Message);
}
}
}