<Window x:Class="Hipot_Sequence_Editor.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:local="clr-namespace:Hipot_Sequence_Editor"
        xmlns:viewModels="clr-namespace:Hipot_Sequence_Editor"
        xmlns:views="clr-namespace:Hipot_Sequence_Editor.Views"
        mc:Ignorable="d"
        Title="MainWindow" Height="677.538" Width="896.456" Name="mainWindow" Loaded="mainWindow_Loaded">

    <Window.DataContext>
        <local:VM_Main></local:VM_Main>
    </Window.DataContext>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="25*"/>
            <RowDefinition Height="299*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="211*"/>
            <ColumnDefinition Width="86*"/>
        </Grid.ColumnDefinitions>
        <TreeView x:Name="treeView" Grid.Column="1" HorizontalAlignment="Left" Height="628" Margin="10.2,10,0,0" VerticalAlignment="Top" Width="237" Grid.RowSpan="2" ItemsSource="{Binding Parts}" SelectedItemChanged="TreeView_OnSelectedItemChanged">
            <TreeView.Resources>

                <HierarchicalDataTemplate x:Name="PartLevel" DataType="{x:Type viewModels:VM_Part}" ItemsSource="{Binding VM_Steps}">
                    <StackPanel Orientation="Horizontal">

                        <TextBlock Text="{Binding SequenceNumber}" />
                        <TextBlock Text=" - "></TextBlock>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </HierarchicalDataTemplate>
                <DataTemplate DataType="{x:Type viewModels:VM_Step}">
                    <StackPanel Orientation="Horizontal">
                        <CheckBox Visibility="{Binding Path=DataContext.CheckMarksVisible, ElementName=PartLevel}"></CheckBox>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </DataTemplate>
            </TreeView.Resources>
        </TreeView>

        <ContentControl Grid.Row="1" Grid.Column="0"  x:Name="ContentPanel" Content="{Binding TreeViewSelectedItem}">
            <ContentControl.Resources>
                <DataTemplate DataType="{x:Type local:VM_Part}">
                    <Label Content="{Binding Name}"></Label>
                </DataTemplate>
                <DataTemplate DataType="{x:Type local:VM_Step}">
                    <views:StepEditorView/>
                </DataTemplate>
            </ContentControl.Resources>
        </ContentControl>

    </Grid>
</Window>

using System.Collections.ObjectModel;
using System.Windows;


namespace Hipot_Sequence_Editor
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        private VM_Main _viewModel;

        public MainWindow()
        {
            InitializeComponent();

            _viewModel = (VM_Main)DataContext;

        }

        private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
            _viewModel.TreeViewSelectedItem = e.NewValue;
        }

        private void mainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            _viewModel.Parts = new ObservableCollection<VM_Part>
            {
                new VM_Part()
                {
                    Name = "Sequence 1",
                    SequenceNumber = 1,
                    VM_Steps = new ObservableCollection<VM_Step>()
                    {
                        new VM_Step() {
                            Name = "Step 1",
                            TestType = TestType.DCW,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                Voltage = 50,
                                RampTime = 33,
                                DwellTime = 20,
                                TestTimeResistance = 30,
                            }
                        },
                        new VM_Step() {
                            Name = "Step 2",
                            TestType = TestType.DCW,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                Voltage = 55,
                                RampTime = 34,
                                DwellTime = 23,
                                TestTimeResistance = 23,
                            }
                        },
                        new VM_Step() {
                            Name = "Step 3",
                            TestType = TestType.LOWOHM,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                TestTimeResistance = 30,
                                MaxResistance = 100
                            }
                        }
                    }
                },
                new VM_Part()
                {
                    Name = "Sequence 2",
                    SequenceNumber = 2,
                    VM_Steps = new ObservableCollection<VM_Step>()
                    {
                        new VM_Step() {
                            Name = "Step 1",
                            TestType = TestType.DCW,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                Voltage = 23,
                                RampTime = 21,
                                DwellTime = 10,
                                TestTimeResistance = 05,
                            }
                        },
                        new VM_Step() {
                            Name = "Step 2",
                            TestType = TestType.DCW,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                Voltage = 55,
                                RampTime = 56,
                                DwellTime = 53,
                                TestTimeResistance = 46,
                            }
                        },
                        new VM_Step() {
                            Name = "Step 3",
                            TestType = TestType.LOWOHM,
                            VM_Step_Test = new VM_Step_Test()
                            {
                                TestTimeResistance = 989,
                                MaxResistance = 75
                            }
                        }
                    }
                }
            };
        }
    }
}

<UserControl x:Class="Hipot_Sequence_Editor.Views.StepEditorView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:dataModel="clr-namespace:Hardware.DataModel;assembly=Vitrek-Library"
             xmlns:uiConverters="clr-namespace:Hipot_Sequence_Editor.UI_Converters"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <uiConverters:DoubleStringConverter  x:Key="DoubleStringConverter" />
        <uiConverters:EnumSelectedConverter x:Key="EnumSelectedConverter" />
    </UserControl.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="25"/>
            <RowDefinition Height="100"/>

        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <WrapPanel Grid.Row="0">
            <Label>Step: </Label>
            <Label Content="{Binding Name}"></Label>
        </WrapPanel>
        <TabControl Grid.Row="1">
            <TabItem Header="Resistance" IsSelected="{Binding VM_Step_Test.vTestType, Converter={StaticResource EnumSelectedConverter}, ConverterParameter={x:Static dataModel:TestType.LOWOHM}}">
                <WrapPanel>
                    <WrapPanel>
                        <Label Content="Resistance"></Label>
                        <TextBox Width="50" Text="{Binding VM_Step_Test.MaxResistance, Converter={StaticResource DoubleStringConverter}}"></TextBox>
                        <Label Content="Ω"></Label>
                    </WrapPanel>
                    <WrapPanel>
                        <Label Content="Dwell Time"></Label>
                        <TextBox Width="50" Text="{Binding VM_Step_Test.TestTimeResistance, Converter={StaticResource DoubleStringConverter}}"></TextBox>
                        <Label Content="mSec"></Label>
                    </WrapPanel>
                </WrapPanel>
            </TabItem>
            <TabItem Header="DC Hipot" IsSelected="{Binding VM_Step_Test.vTestType, Converter={StaticResource EnumSelectedConverter}, ConverterParameter={x:Static dataModel:TestType.DCW}}" Height="22" VerticalAlignment="Top">
                <WrapPanel>
                    <WrapPanel>
                        <Label Content="Voltage"></Label>
                        <TextBox Width="50" Text="{Binding VM_Step_Test.Voltage, Converter={StaticResource DoubleStringConverter}}"></TextBox>
                        <Label Content="kV"></Label>
                    </WrapPanel>
                    <WrapPanel>
                        <Label Content="Ramp Time"></Label>
                        <TextBox Width="50" Text="{Binding VM_Step_Test.RampTime, Converter={StaticResource DoubleStringConverter}}"></TextBox>
                        <Label Content="mSec"></Label>
                    </WrapPanel>
                    <WrapPanel>
                        <Label Content="Dwell Time"></Label>
                        <TextBox Width="50" Text="{Binding VM_Step_Test.DwellTime, Converter={StaticResource DoubleStringConverter}}"></TextBox>
                        <Label Content="mSec"></Label>
                    </WrapPanel>
                </WrapPanel>
            </TabItem>

        </TabControl>
    </Grid>
</UserControl>

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using PropertyChanged;

namespace Hipot_Sequence_Editor
{
    [AddINotifyPropertyChangedInterface]
    public class VM_Main
    {

        private object _treeViewSelectedItem;

        public ObservableCollection<VM_Part> Parts { get; set; }

        public object TreeViewSelectedItem
        {
            get => _treeViewSelectedItem;
            set { _treeViewSelectedItem = value; OnSelectedNodeChanged(value); }
        }

        public VM_Part SelectedPartForUI { get; set; }

        public VM_Step SelectedStepForUI { get; set; }

        public VM_Step_Test SelectedTestStepForUI { get; set; }

        private void OnSelectedNodeChanged(object node)
        {
            switch (node)
            {
                case VM_Part vmpart:
                    SelectedPartForUI = vmpart;
                    break;
                case VM_Step vmstep:
                    SelectedStepForUI = vmstep;
                    break;
                default:
                    throw new NotImplementedException();

            }

        }
    }

    public enum TestType
    {
        [Description("AC Hipot")]
        ACW,
        [Description("DC Hipot")]
        DCW,
        [Description("Resistance")]
        LOWOHM
    }

    [AddINotifyPropertyChangedInterface]
    public class VM_Part
    {
        public int SequenceNumber { get; set; }
        public string Name { get; set; }
        public ObservableCollection<VM_Step> VM_Steps { get; set; }
        public bool IsSelected { get; set; }
        public bool CheckMarksVisible { get; set; }
    }

    [AddINotifyPropertyChangedInterface]
    public class VM_Step
    {
        public string Name { get; set; }
        public TestType TestType { get; set; }
        public VM_Step_Test VM_Step_Test { get; set; }
        public bool IsSelected { get; set; }

    }

    [AddINotifyPropertyChangedInterface]
    public class VM_Step_Test
    {
        public TestType vTestType { get; set; }
        public double RampTime { get; set; }

        public double DwellTime { get; set; }

        public double Voltage { get; set; }

        public double TestTimeResistance { get; set; }
        public double MaxResistance { get; set; }
    }

}

using System.Windows.Data;

namespace Hipot_Sequence_Editor.UI_Converters
{

    public class EnumSelectedConverter : IValueConverter
    {
        public object Convert(object value, Type targetType,
            object parameter, System.Globalization.CultureInfo culture)
        {
            if (value == null || parameter == null) return false;
            TestType vmType = (TestType) value;
            TestType viewType = (TestType) parameter;

            return vmType == viewType;
        }

        public object ConvertBack(object value, Type targetType,
            object parameter, System.Globalization.CultureInfo culture)
        {
            if (value == null || parameter == null) return false;

            bool isSelected = (bool) value;
            if (!isSelected) return false;

            TestType vTestType = (TestType) parameter;

            return vTestType;
        }
    }
}

using System;
using System.Windows.Data;

namespace Hipot_Sequence_Editor.UI_Converters
{

    public class DoubleStringConverter : IValueConverter
    {
        private string user_string = null;

        public object Convert(object value, Type targetType,
            object parameter, System.Globalization.CultureInfo culture)
        {
            if (user_string != null)
            {
                return user_string;
            }

            double number = (double)value;
            return string.Format(System.Globalization.CultureInfo.CurrentCulture, "{0}", number);
        }

        public object ConvertBack(object value, Type targetType,
            object parameter, System.Globalization.CultureInfo culture)
        {
            string s_value = value.ToString();
            double result = 0;

            System.Text.RegularExpressions.Regex nonNumericCharacters = new System.Text.RegularExpressions.Regex(@"[^0-9.]");
            string numericOnlyString = nonNumericCharacters.Replace(s_value, String.Empty);

            if (!double.TryParse(numericOnlyString, System.Globalization.NumberStyles.Number,
                System.Globalization.CultureInfo.CurrentCulture, out result))
               return null;

            user_string = s_value;

            return result;
        }
    }
}