feat: support dynamic form group generation, add demo.

demo/Ursa.Demo/DataTemplates/FormDataTemplateSelector.cs

@@ -0,0 +1,24 @@
+using Avalonia.Controls;
+using Avalonia.Controls.Templates;
+using Ursa.Demo.ViewModels;
+
+namespace Ursa.Demo.Converters;
+
+public class FormDataTemplateSelector: ResourceDictionary, IDataTemplate
+{
+    public Control? Build(object? param)
+    {
+        if (param is null) return null;
+        var type = param.GetType();
+        if (this.TryGetResource(type, null, out var template) && template is IDataTemplate dataTemplate)
+        {
+            return dataTemplate.Build(param);
+        }
+        return null;
+    }
+
+    public bool Match(object? data)
+    {
+        return data is IFromItemViewModel;
+    }
+}

demo/Ursa.Demo/Pages/FormDemo.axaml

@@ -7,6 +7,7 @@
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:u="https://irihi.tech/ursa"
     xmlns:vm="clr-namespace:Ursa.Demo.ViewModels;assembly=Ursa.Demo"
+    xmlns:converters="clr-namespace:Ursa.Demo.Converters"
     d:DesignHeight="450"
     d:DesignWidth="800"
     x:CompileBindings="True"
@@ -50,6 +51,31 @@
                 <TextBox Width="300" u:FormItem.Label="Name" Text="{Binding  Name}"/>
                 <TextBox Width="300" u:FormItem.Label="Email" Text="{Binding Email}" />
             </u:Form>
+            <u:Divider Content="MVVM setup for dynamic items. " />
+            <u:Form ItemsSource="{Binding FormGroups}" HorizontalAlignment="Stretch" LabelPosition="Left" LabelWidth="*">
+                <u:Form.Styles>
+                    <Style Selector="u|FormGroup" x:DataType="vm:IFormGroupViewModel">
+                        <Setter Property="Header" Value="{Binding Title}" />
+                        <Setter Property="ItemsSource" Value="{Binding Items}" />
+                    </Style>
+                    <Style Selector="u|FormItem" x:DataType="vm:IFromItemViewModel">
+                        <Setter Property="Label" Value="{Binding Label}" />
+                    </Style>
+                </u:Form.Styles>
+                <u:Form.ItemTemplate>
+                    <converters:FormDataTemplateSelector>
+                        <DataTemplate x:Key="{x:Type vm:FormTextViewModel}" DataType="vm:FormTextViewModel">
+                            <TextBox Text="{Binding Value}"/>
+                        </DataTemplate>
+                        <DataTemplate x:Key="{x:Type vm:FormAgeViewModel}" DataType="vm:FormAgeViewModel">
+                            <u:NumericUIntUpDown Value="{Binding Age}"/>
+                        </DataTemplate>
+                        <DataTemplate x:Key="{x:Type vm:FormDateRangeViewModel}" DataType="vm:FormDateRangeViewModel">
+                            <u:DateRangePicker SelectedStartDate="{Binding Start}" SelectedEndDate="{Binding End}"/>
+                        </DataTemplate>
+                    </converters:FormDataTemplateSelector>
+                </u:Form.ItemTemplate>
+            </u:Form>
         </StackPanel>
     </ScrollViewer>
 </UserControl>

demo/Ursa.Demo/ViewModels/FormDemoViewModel.cs

@@ -1,6 +1,8 @@
 using System;
+using System.Collections.ObjectModel;
 using System.ComponentModel.DataAnnotations;
 using CommunityToolkit.Mvvm.ComponentModel;
+using Irihi.Avalonia.Shared.Contracts;
 
 namespace Ursa.Demo.ViewModels;
 
@@ -11,13 +13,48 @@ public partial class FormDemoViewModel : ObservableObject
     public FormDemoViewModel()
     {
         Model = new DataModel();
+        FormGroups = new ObservableCollection<IFormElement>
+        {
+            new FormGroupViewModel
+            {
+                Title = "Basic Information",
+                Items = new ObservableCollection<IFromItemViewModel>
+                {
+                    new FormTextViewModel { Label = "Name" },
+                    new FormAgeViewModel { Label = "Age" },
+                    new FormTextViewModel { Label = "Email" }
+                }
+            },
+            new FormGroupViewModel
+            {
+                Title = "Education Information",
+                Items = new ObservableCollection<IFromItemViewModel>
+                {
+                    new FormTextViewModel { Label = "College" },
+                    new FormDateRangeViewModel { Label = "Study Time" }
+                }
+            },
+            new FormTextViewModel(){ Label = "Other" }
+        };
     }
+
+    public ObservableCollection<IFormElement> FormGroups { get; set; }
 }
 
-public partial class DataModel : ObservableObject
+public class DataModel : ObservableObject
 {
+    private DateTime _date;
+
+    private string _email = string.Empty;
     private string _name = string.Empty;
 
+    private double _number;
+
+    public DataModel()
+    {
+        Date = DateTime.Today;
+    }
+
     [MinLength(10)]
     public string Name
     {
@@ -25,8 +62,6 @@ public partial class DataModel : ObservableObject
         set => SetProperty(ref _name, value);
     }
 
-    private double _number;
-
     [Range(0.0, 10.0)]
     public double Number
     {
@@ -34,8 +69,6 @@ public partial class DataModel : ObservableObject
         set => SetProperty(ref _number, value);
     }
 
-    private string _email = string.Empty;
-
     [EmailAddress]
     public string Email
     {
@@ -43,16 +76,50 @@ public partial class DataModel : ObservableObject
         set => SetProperty(ref _email, value);
     }
 
-    private DateTime _date;
-
     public DateTime Date
     {
         get => _date;
         set => SetProperty(ref _date, value);
     }
+}
 
-    public DataModel()
+public interface IFormElement
-    {
+{
-        Date = DateTime.Today;
+    
-    }
+}
+
+public interface IFormGroupViewModel : IFormGroup, IFormElement
+{
+    public string? Title { get; set; }
+    public ObservableCollection<IFromItemViewModel> Items { get; set; }
+}
+
+public interface IFromItemViewModel: IFormElement
+{
+    public string? Label { get; set; }
+}
+
+public partial class FormGroupViewModel : ObservableObject, IFormGroupViewModel
+{
+    [ObservableProperty] private string? _title;
+    public ObservableCollection<IFromItemViewModel> Items { get; set; } = [];
+}
+
+public partial class FormTextViewModel : ObservableObject, IFromItemViewModel
+{
+    [ObservableProperty] private string? _label;
+    [ObservableProperty] private string? _value;
+}
+
+public partial class FormAgeViewModel : ObservableObject, IFromItemViewModel
+{
+    [ObservableProperty] private uint? _age;
+    [ObservableProperty] private string? _label;
+}
+
+public partial class FormDateRangeViewModel : ObservableObject, IFromItemViewModel
+{
+    [ObservableProperty] private DateTime? _end;
+    [ObservableProperty] private string? _label;
+    [ObservableProperty] private DateTime? _start;
 }

src/Ursa.Themes.Semi/Controls/Form.axaml

@@ -70,6 +70,7 @@
                     </StackPanel>
                     <ContentPresenter
                         Name="PART_ContentPresenter"
+                        ContentTemplate="{TemplateBinding ContentTemplate}"
                         Content="{TemplateBinding Content}" />
                 </StackPanel>
             </ControlTemplate>
@@ -111,6 +112,7 @@
                             Grid.Column="1"
                             VerticalAlignment="Stretch"
                             VerticalContentAlignment="Center"
+                            ContentTemplate="{TemplateBinding ContentTemplate}"
                             Content="{TemplateBinding Content}" />
                     </Grid>
                 </ControlTemplate>
@@ -120,6 +122,7 @@
             <Setter Property="Template">
                 <ControlTemplate TargetType="u:FormItem">
                     <ContentPresenter
+                        ContentTemplate="{TemplateBinding ContentTemplate}"
                         Content="{TemplateBinding Content}" />
                 </ControlTemplate>
             </Setter>

src/Ursa/Controls/Form/Form.cs

@@ -2,6 +2,7 @@
 using Avalonia.Controls;
 using Avalonia.Controls.Metadata;
 using Avalonia.Layout;
+using Irihi.Avalonia.Shared.Contracts;
 using Ursa.Common;
 
 namespace Ursa.Controls;
@@ -64,7 +65,11 @@ public class Form: ItemsControl
     
     protected override Control CreateContainerForItemOverride(object? item, int index, object? recycleKey)
     {
-        if (item is not Control control) return new FormItem();
+        if (item is not Control control)
+        {
+            if (item is IFormGroup) return new FormGroup();
+            return new FormItem();
+        }
         return new FormItem()
         {
             Content = control,
@@ -73,4 +78,17 @@ public class Form: ItemsControl
             [!FormItem.NoLabelProperty] = control[!FormItem.NoLabelProperty],
         };
     }
+
+    protected override void PrepareContainerForItemOverride(Control container, object? item, int index)
+    {
+        base.PrepareContainerForItemOverride(container, item, index);
+        if(container is FormItem formItem && !formItem.IsSet(ContentControl.ContentTemplateProperty))
+        {
+            formItem.ContentTemplate = ItemTemplate;
+        }
+        if (container is FormGroup group && !group.IsSet(FormGroup.ItemTemplateProperty))
+        {
+            group.ItemTemplate = ItemTemplate;
+        }
+    }
 }

src/Ursa/Controls/Form/FormGroup.cs

@@ -21,5 +21,13 @@ public class FormGroup: HeaderedItemsControl
             [!FormItem.IsRequiredProperty] = control[!FormItem.IsRequiredProperty],
         };
     }
-    
+
+    protected override void PrepareContainerForItemOverride(Control container, object? item, int index)
+    {
+        base.PrepareContainerForItemOverride(container, item, index);
+        if (container is FormItem formItem && !formItem.IsSet(ContentControl.ContentTemplateProperty))
+        {
+            formItem.ContentTemplate = ItemTemplate;
+        }
+    }
 }