How do I use generic base class instead of window in wpf? - wpf

Question

How do I make this work?
public partial class MyWindow : View<MyViewModel>
{
}
where View is defined as
public class View<T> : Window where T : IViewModel, new()
{
}
XAML:
<local:View
x:Class="Project.MyWindow"
x:TypeArguments="ViewModels:MyViewModel"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
xmlns:ViewModels="clr-namespace:Mynamespace.ViewModels;assembly=Mynamespace.ViewModels"
xmlns:local="clr-namespace:Project"
>
I get this error... The name View does not exist in the namespace Project... which of course it does.
and I get this error which really confuses me... The property "TypeArguments" does not exist in the "http://schemas.microsoft.com/winfx/2006/xaml" namespace... which of course it does.
Any clues on how to use generics as a base class for windows in wpf?

Answer 1

The answer to this question is to never use generics with xaml. There is always a better way or a workaround. See the comments on the original post.
EDIT!
Thanks to Micky Duncan (see the comments above) the correct answer to this question can be found by investigating these two links:
http://msdn.microsoft.com/en-us/library/ms741843(v=vs.110).aspx
http://www.codeproject.com/Articles/37317/Generic-Support-In-XAML

Answer 2

This is an Old Topic, but as I came around and others might to:
I don't know since when, but tested in .net 6.0
The approach was right, but without knowing which project settings the questioner used it is hard to say what went wrong.
yes i know it's ugly, but i have to admit is was a prove of concept prototyp
SAMPLE XAML:
<base:ApplicationTabItem x:TypeArguments="entries:ArtikelEntry,vms:ArtikelTabViewModel"
x:Class="S2_Management.DesktopApp.UIElements.AppTabs.ArtikelTab"
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:S2_Management.DesktopApp.UIElements.AppTabs"
mc:Ignorable="d"
xmlns:vms ="clr-namespace:S2_Management.DesktopApp.ViewModels"
xmlns:values="clr-namespace:S2_Management.CoreLib.ConstantValues;assembly=S2-Management.CoreLib"
xmlns:entries="clr-namespace:S2_Management.CoreLib.Tables;assembly=S2-Management.CoreLib"
xmlns:base="clr-namespace:S2_Management.DesktopApp.UIElements.Base"
d:DataContext="{d:DesignInstance Type=vms:ArtikelTabViewModel, IsDesignTimeCreatable=true}"
d:DesignHeight="450" d:DesignWidth="800"
>
<TabItem.Header>
<Label Content="{Binding FQ_TabName}"/>
</TabItem.Header>
<Grid KeyUp="OnKeyUp">
<DataGrid ItemsSource="{Binding ItemListe}" AutoGenerateColumns="False" CanUserAddRows="False" CanUserDeleteRows="False" SelectedItem="{Binding SelectedItem}">
<DataGrid.Resources>
<Style TargetType="DataGridRow">
<EventSetter Event="MouseDoubleClick" Handler="ItemDoubleClick"/>
</Style>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTextColumn Header="{x:Static values:ConstantValueStore.ArtikelTabGridBezeichnungTitle}" Binding="{Binding Artikel_Bezeichnung}" IsReadOnly="True" SortDirection="Ascending" />
<DataGridTextColumn Header="{x:Static values:ConstantValueStore.ArtikelTabGridEinheitenTitle}" Binding="{Binding Einheit.Einheiten_Bezeichnung}" IsReadOnly="True"/>
<DataGridTextColumn Header="{x:Static values:ConstantValueStore.ArtikelTabGridKategorieTitle}" Binding="{Binding ArtikelKategorie.ArtikelKategorien_Bezeichnung}" IsReadOnly="True"/>
<DataGridTextColumn Header="{x:Static values:ConstantValueStore.ArtikelTabGridPreisGruppeTitle}" Binding="{Binding Preisgruppe.Preisgruppen_Bezeichnung}" IsReadOnly="True"/>
</DataGrid.Columns>
</DataGrid>
</Grid>
</base:ApplicationTabItem>
Sample CodeBehind
namespace S2_Management.DesktopApp.UIElements.AppTabs
{
/// <summary>
/// logic for ArtikelTab.xaml
/// </summary>
public partial class ArtikelTab //: ApplicationTabItem<ArtikelEntry, ArtikelTabViewModel>
{
public ArtikelTab()
{
InitializeComponent();
this.DataContext = _vm = getTabViewModel();
}
}
}
Sample BaseClass:
namespace S2_Management.DesktopApp.UIElements.Base
{
public class ApplicationTabItem<ItemType, TVMType> : TabItem, IApplicationTabItem
where TVMType : ITabViewModel<ItemType>, new()
{
protected TVMType? _vm;
protected TVMType getTabViewModel()
{
return new TVMType() { OwnTabItem = this };
}
public virtual RibbonTab? GetRibbonTab()
{
return _vm?.GetRibbonTab();
}
protected void ItemDoubleClick(object sender, MouseButtonEventArgs? e)
{
_vm?.OpenSelectedItemFor(CRUDModus.Read);
}
protected void OnKeyUp(object sender, KeyEventArgs e)
{
if ((e.KeyboardDevice.Modifiers & ModifierKeys.Control) != 0)
{
switch (e.Key)
{
case Key.D:
_vm?.CopyCommand?.Execute(null);
break;
case Key.N:
_vm?.CreateNewCommand?.Execute(null);
break;
}
}
else
{
switch (e.Key)
{
case Key.Escape:
if (_vm != null) _vm.SelectedItem = default;
break;
case Key.Enter:
ItemDoubleClick(this, null);
break;
case Key.Delete:
case Key.Back:
_vm?.DeleteCommand?.Execute(null);
break;
}
}
}
}
}
Explanation
public class ApplicationTabItem<ItemType, TVMType> : TabItem, IApplicationTabItem
where TVMType : ITabViewModel<ItemType>, new()
This is the superclass, which inherits from TabItem. As we all, should, know:
TabItem
is an UIElement and brings everything we need!
<base:ApplicationTabItem x:TypeArguments="entries:ArtikelEntry,vms:ArtikelTabViewModel"
is what say's hey inherit please!
IMPORTANT:
public partial class ArtikelTab //: ApplicationTabItem<ArtikelEntry, ArtikelTabViewModel>
Original we could inherit in code behind as well, which is :
redundant
Bad style, because you need to change things on two places
but: better and faster readable
but as of today there is an open BUG:
Inheriting from a generic type within a code behind file will fail during the [whatever].xaml.g.s generation. So be VERY sure to remove that inherit from code behind, or at leased put it on comment!!!
Link to MS Blog Page on that topic, but in a very early state of support:
https://learn.microsoft.com/en-us/archive/blogs/mikehillberg/limited-generics-support-in-xaml