namespace WpfApp14
{
    using System;
    using System.ComponentModel;
    using System.Windows;
    using System.Collections.ObjectModel;

    public sealed class GridValueViewModel : INotifyPropertyChanged
    {
        private string someValue = string.Empty;

        public GridValueViewModel(string someValue)
        {
            this.SomeValue = someValue;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public string SomeValue
        {
            get
            {
                return this.someValue;
            }

            set
            {
                value = value ?? string.Empty;
                if (this.SomeValue != value)
                {
                    this.someValue = value;
                    this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(this.SomeValue)));
                }
            }
        }

        public DateTime? DateValue
        {
            get
            {
                if (DateTime.TryParse(this.SomeValue, out var value))
                {
                    return value;
                }

                return null;
            }

            set
            {
                if (value == null)
                {
                    this.SomeValue = string.Empty;
                    return;
                }

                this.SomeValue = value.ToString();
            }
        }

        public ObservableCollection<string> SomeValueItems { get; } = new ObservableCollection<string>(
            new[]
            {
                "cat",
                "dog",
                "bird"
            });
        
    }

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            this.InitializeComponent();
            this.DataContext = this;
        }

        public ObservableCollection<GridValueViewModel> Values { get; } = new ObservableCollection<GridValueViewModel>(
            new[]
            {
                new GridValueViewModel("cat"),
                new GridValueViewModel("dog"),
                new GridValueViewModel("bird")
            });
    }
}

<Window x:Class="WpfApp14.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <telerik:RadGridView
        AutoGenerateColumns="False"
        ItemsSource="{Binding Values, Mode=OneWay}">
        <telerik:RadGridView.Columns>
            <telerik:GridViewDataColumn
                Header="Column 1">
                <telerik:GridViewDataColumn.CellTemplate>
                    <DataTemplate>
                        <Label
                            Content="{Binding SomeValue}" />
                    </DataTemplate>
                </telerik:GridViewDataColumn.CellTemplate>
                <telerik:GridViewDataColumn.CellEditTemplate>
                    <DataTemplate>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition
                                    Width="*" />
                            </Grid.ColumnDefinitions>
                            <TextBox
                                Grid.Column="0"
                                Text="{Binding SomeValue, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
                                Visibility="Collapsed" />
                            <telerik:RadComboBox
                                Grid.Column="0"
                                HorizontalAlignment="Stretch"
                                IsEditable="False"
                                ItemsSource="{Binding SomeValueItems}"
                                SelectedItem="{Binding SomeValue}" />
                            <telerik:RadDateTimePicker
                                Grid.Column="0"
                                HorizontalAlignment="Stretch"
                                InputMode="DatePicker"
                                DateTimeWatermarkContent="{x:Null}"
                                SelectedValue="{Binding DateValue, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
                                Visibility="Collapsed" />
                        </Grid>
                    </DataTemplate>
                </telerik:GridViewDataColumn.CellEditTemplate>
            </telerik:GridViewDataColumn>
        </telerik:RadGridView.Columns>
    </telerik:RadGridView>
</Window>