I want to access runtime the value by which the user filters.
===ADMIN EDIT===
Use the OnRead event handler to access the filter value:
private async Task ReadItems(ComboBoxReadEventArgs args)
{
if (args.Request.Filters.Count > 0)
{
Telerik.DataSource.FilterDescriptor filter = args.Request.Filters[0] as Telerik.DataSource.FilterDescriptor;
string userInput = filter.Value.ToString();
...
}
...
}