<ContentPage.Resources>
    <DataTemplate x:Key="EmptyContentTemplate">
        <Label Margin="10" TextColor="Red" HorizontalOptions="Center" Text="No data to display" />
    </DataTemplate>
</ContentPage.Resources>

<Grid RowDefinitions="Auto, *">
    <telerik:RadUniformGrid>
        <telerik:RadTemplatedButton Content="Clear temsSource" Clicked="OnCounterClicked" />
        <telerik:RadTemplatedButton Content="Add Item" Clicked="OnAddClicked"/>
    </telerik:RadUniformGrid>
    <telerik:RadDataGrid Grid.Row="2"
                            x:Name="dataGrid"
                            ItemsSource="{Binding Collection}"
                            EmptyContentTemplate="{StaticResource EmptyContentTemplate}"
                            EmptyContentDisplayMode="ItemsSourceNullOrEmpty" />
</Grid>

public partial class MainPage : ContentPage
{
    int count = 0;
    MainViewModel vm;
    public MainPage()
    {
        InitializeComponent();
        this.vm = new MainViewModel();
        this.BindingContext = this.vm;
    }
    private void OnCounterClicked(object? sender, EventArgs e)
    {
        this.vm.Collection.Clear();
         this.dataGrid.EmptyContentTemplate = this.Resources["EmptyContentTemplate"] as DataTemplate;
    }

    private void OnAddClicked(object sender, EventArgs e)
    {
        this.vm.Collection.Add(new VMData { Value = "rwerwerwer" });
        this.dataGrid.EmptyContentTemplate = null;
    }
}