<telerik:RadTimeline ItemsSource="{Binding Orders}"
					 PeriodStart="01/01/2018"
					 PeriodEnd="01/01/2019"
					 StartPath="Period.Start"
					 DurationPath="Period.Duration"/>

<telerik:RadTimeline ItemsSource="{Binding Orders}"
					 PeriodStart="01/01/2018"
					 PeriodEnd="01/01/2019"
					 StartPath="Period.Start"
					 DurationPath="Period.Duration"/>

StartPath="Period.Start"
DurationPath="Period.Duration"

<telerik:RadTimeline ItemsSource="{Binding MyInvisibleItemsControl.VisualItems}"
    PeriodStart="01/01/2018"
    PeriodEnd="01/01/2019"
    StartPath="AnimatedStart"
    DurationPath="AnimatedDuration"/>

<ItemsControl ItemSource="{Binding Orders}" Visibility="Collapsed" Name="MyInvisibleItemsControl">
    <ItemsPanel>
        <Grid Name="XYZ"/>
    <ItemsPanel>
<ItemsControl>

<DataTemplate DataType="{x:Type vm:ConfirmAddOrderVM}">
    тут UI для confirm add
<DataTemplate/>

<DataTemplate DataType="{x:Type vm:ConfirmAddOrderVM}">
    <view:ConfirmAddUserControl/>
<DataTemplate/>

<DataTemplate DataType="{x:Type vm:ConfirmAddOrderVM}">
    <view:ConfirmAddUserControl AcceptCommand="{Binding MyAcceptCommand}"/>
<DataTemplate/>

public static class EnumerableEx
{
    public static List<T> ToList<T>(this IEnumerable<T> source, int capacity)
    {
        if (source is null) throw new ArgumentNullException(nameof(source));
        var list = new List<T>(capacity);
        list.AddRange(source);
        return list;
    }
}

[MemoryDiagnoser]
public class ToListTests
{
    private int count = 1000;
    private static Random random = new Random();

    private IEnumerable<int> RandomSeq()
    {
        while (true) yield return random.Next();
    }

    [Benchmark]
    public List<int> ToListFromBcl()
    {
        return RandomSeq().Take(count).ToList();
    }

    [Benchmark]
    public List<int> ToListWithCapacity()
    {
        return RandomSeq().Take(count).ToList(count);
    }
}

``` ini

BenchmarkDotNet=v0.10.13, OS=Windows 10 Redstone 3 [1709, Fall Creators Update] (10.0.16299.248)
Intel Core i7-7700HQ CPU 2.80GHz (Kaby Lake), 1 CPU, 8 logical cores and 4 physical cores
Frequency=2742193 Hz, Resolution=364.6716 ns, Timer=TSC
  [Host]     : .NET Framework 4.7.1 (CLR 4.0.30319.42000), 32bit LegacyJIT-v4.7.2633.0
  DefaultJob : .NET Framework 4.7.1 (CLR 4.0.30319.42000), 32bit LegacyJIT-v4.7.2633.0


```
|             Method |     Mean |     Error |    StdDev |  Gen 0 | Allocated |

var orderConfirmFunctionalityVM = new OrderConfirmFuctionalityVM(newOrder);
orderConfirmFunctionalityVM.AcceptRequest += (order) => { CurrentOrderFunctionalityVM = null; OrdersVM.AcceptOrder(order); };
orderConfirmFunctionalityVM.CancelRequest += (order) => { CurrentOrderFunctionalityVM = null; OrdersVM.CancelOrder(order); };
CurrentOrderFunctionalityVM = orderConfirmFunctionalityVM;