added SendReceiveViewModel and according View,

moved StartupHelpers to new Common project,
added TabControl to ShellView

Common/Common.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0" />
+  </ItemGroup>
+
+</Project>

Common/StartupHelpers/AbstractFactory.cs

@@ -0,0 +1,24 @@
+namespace Common.StartupHelpers;
+
+public class AbstractFactory<T> : IAbstractFactory<T>
+{
+    private readonly Func<T> factory;
+
+    /// <summary>
+    /// Constructor for Abstract Factory.
+    /// </summary>
+    /// <param name="factory">Function of the factory</param>
+    public AbstractFactory(Func<T> factory)
+    {
+        this.factory = factory;
+    }
+
+    /// <summary>
+    /// Executes factory function and returns it.
+    /// </summary>
+    /// <returns>Factory</returns>
+    public T Create()
+    {
+        return factory();
+    }
+}

Common/StartupHelpers/IAbstractFactory.cs

@@ -0,0 +1,6 @@
+namespace Common.StartupHelpers;
+
+public interface IAbstractFactory<T>
+{
+    T Create();
+}

Common/StartupHelpers/ServiceExtensions.cs

@@ -0,0 +1,22 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Common.StartupHelpers;
+
+public static class ServiceExtensions
+{
+    /// <summary>
+    /// Adds a factory for subcontrols to be created.
+    /// For example a UserControl can be instanciated using this Service.
+    /// </summary>
+    /// <typeparam name="TSubControl">type of the subcontrol</typeparam>
+    /// <param name="services">existing service collection</param>
+    public static void AddSubControlFactory<TSubControl>(this IServiceCollection services) where TSubControl : class
+    {
+        // add to DI: the subcontrol itself
+        services.AddTransient<TSubControl>();
+        // add to DI: Func of that subcontrol, that will create the subcontrol
+        services.AddSingleton<Func<TSubControl>>(x => () => x.GetService<TSubControl>()!);
+        // add to DI: Factory for the subcontrol
+        services.AddSingleton<IAbstractFactory<TSubControl>, AbstractFactory<TSubControl>>();
+    }
+}

MultiTerm.Core/MultiTerm.Core.csproj

@@ -14,4 +14,8 @@
     <PackageReference Include="CommunityToolkit.Mvvm" Version="8.1.0" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.csproj" />
+  </ItemGroup>
+
 </Project>

MultiTerm.Core/ViewModel/ITerminalViewModel.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace MultiTerm.Core.ViewModel;
+
+public interface ITerminalViewModel
+{
+    string Title { get; }
+}

MultiTerm.Core/ViewModel/SendReceiveViewModel.cs

@@ -0,0 +1,10 @@
+using System;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace MultiTerm.Core.ViewModel;
+
+[ObservableObject]
+public partial class SendReceiveViewModel : TerminalViewModel
+{
+    public override string Title => "SendReceive Tab";
+}

MultiTerm.Core/ViewModel/ShellViewModel.cs

@@ -1,9 +1,38 @@
-using CommunityToolkit.Mvvm.ComponentModel;
+using Common.StartupHelpers;
+using CommunityToolkit.Mvvm.ComponentModel;
+using System.Collections.ObjectModel;
 
 namespace MultiTerm.Core.ViewModel;
 
 public partial class ShellViewModel : ObservableObject
 {
+    private readonly IAbstractFactory<SendReceiveViewModel> sendReceiveViewModelFactory;
+
     [ObservableProperty]
     private string title = "ShellView Test";
+
+    [ObservableProperty]
+    private ObservableCollection<ITerminalViewModel> terminalViewModels = new();
+
+    [ObservableProperty]
+    private ITerminalViewModel? selectedTerminalViewModel;
+
+    public ShellViewModel(IAbstractFactory<SendReceiveViewModel> sendReceiveViewModelFactory)
+    {
+        this.sendReceiveViewModelFactory = sendReceiveViewModelFactory;
+        // create a new terminal
+        this.AppendTerminal(this.sendReceiveViewModelFactory.Create());
+    }
+
+    public void AppendTerminal(ITerminalViewModel newTerminal)
+    {
+        // guard null value
+        if(newTerminal == null)
+        {
+            return;
+        }
+        // add to collection and set as selected
+        this.TerminalViewModels.Add(newTerminal);
+        this.SelectedTerminalViewModel = newTerminal;
+    } 
 }

MultiTerm.Core/ViewModel/TerminalViewModel.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace MultiTerm.Core.ViewModel;
+
+public abstract class TerminalViewModel : ITerminalViewModel
+{
+    public abstract string Title { get; }
+}

MultiTerm.Wpf/App.xaml.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using MultiTerm.Core.ViewModel;
+using Common.StartupHelpers;
 using System.Windows;
 
 namespace MultiTerm.Wpf;
@@ -19,6 +20,9 @@ public partial class App : Application
 
                 // viewmodels
                 services.AddSingleton<ShellViewModel>();
+
+                // subcontrols
+                services.AddSubControlFactory<SendReceiveViewModel>();
             })
             .Build();
     }

MultiTerm.Wpf/MultiTerm.Wpf.csproj

@@ -13,6 +13,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\Common\Common.csproj" />
     <ProjectReference Include="..\MultiTerm.Core\MultiTerm.Core.csproj" />
   </ItemGroup>
 

MultiTerm.Wpf/View/SendReceiveView.xaml

@@ -0,0 +1,12 @@
+<UserControl x:Class="MultiTerm.Wpf.View.SendReceiveView"
+             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:local="clr-namespace:MultiTerm.Wpf.View"
+             mc:Ignorable="d" 
+             d:DesignHeight="450" d:DesignWidth="800">
+    <Grid>
+            
+    </Grid>
+</UserControl>

MultiTerm.Wpf/View/SendReceiveView.xaml.cs

@@ -0,0 +1,11 @@
+using System.Windows.Controls;
+
+namespace MultiTerm.Wpf.View;
+
+public partial class SendReceiveView : UserControl
+{
+    public SendReceiveView()
+    {
+        InitializeComponent();
+    }
+}

MultiTerm.Wpf/View/ShellView.xaml

@@ -4,9 +4,28 @@
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
              xmlns:local="clr-namespace:MultiTerm.Wpf.View"
+             xmlns:vm="clr-namespace:MultiTerm.Core.ViewModel;assembly=MultiTerm.Core"
+             xmlns:v="clr-namespace:MultiTerm.Wpf.View"
              mc:Ignorable="d" 
              d:DesignHeight="450" d:DesignWidth="800">
     <Grid>
-        <Label Content="{Binding Title}"/>
+        <TabControl
+            x:Name="terminalTabControl"
+            ItemsSource="{Binding TerminalViewModels}"
+            SelectedItem="{Binding SelectedTerminalViewModel}">
+            
+            <TabControl.Resources>
+                <DataTemplate DataType="{x:Type vm:SendReceiveViewModel}">
+                    <v:SendReceiveView/>
+                </DataTemplate>
+            </TabControl.Resources>
+
+            <TabControl.ItemContainerStyle>
+                <Style TargetType="TabItem">
+                    <Setter Property="Header" Value="{Binding Title}" />
+                </Style>
+            </TabControl.ItemContainerStyle>
+
+        </TabControl>
     </Grid>
 </UserControl>

MultiTerm.sln

@@ -3,9 +3,11 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.5.33424.131
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MultiTerm.Wpf", "MultiTerm.Wpf\MultiTerm.Wpf.csproj", "{1C18608F-596A-47ED-9BD6-96E5E52E6E88}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MultiTerm.Wpf", "MultiTerm.Wpf\MultiTerm.Wpf.csproj", "{1C18608F-596A-47ED-9BD6-96E5E52E6E88}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MultiTerm.Core", "MultiTerm.Core\MultiTerm.Core.csproj", "{A4ED5CBB-954E-4F23-B9CB-8E30DF7B8F48}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MultiTerm.Core", "MultiTerm.Core\MultiTerm.Core.csproj", "{A4ED5CBB-954E-4F23-B9CB-8E30DF7B8F48}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Common", "Common\Common.csproj", "{26454190-1B60-46BE-8234-3207FB00D8A4}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -21,6 +23,10 @@ Global
 		{A4ED5CBB-954E-4F23-B9CB-8E30DF7B8F48}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A4ED5CBB-954E-4F23-B9CB-8E30DF7B8F48}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A4ED5CBB-954E-4F23-B9CB-8E30DF7B8F48}.Release|Any CPU.Build.0 = Release|Any CPU
+		{26454190-1B60-46BE-8234-3207FB00D8A4}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{26454190-1B60-46BE-8234-3207FB00D8A4}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{26454190-1B60-46BE-8234-3207FB00D8A4}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{26454190-1B60-46BE-8234-3207FB00D8A4}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE