From 88db01532f70f209af9a1cb90f8bd13ad36fc6bf Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Tue, 4 Jan 2022 16:34:41 +0100
Subject: [PATCH 1/6] Implement CellEditingTemplate

---
 .../DataGridTemplateColumn.cs                 | 32 +++++++++++++++++--
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
index 7e95dd100c..fbdad0a8ad 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
@@ -30,6 +30,20 @@ namespace Avalonia.Controls
             set { SetAndRaise(CellTemplateProperty, ref _cellTemplate, value); }
         }
 
+        private IDataTemplate _cellEditingCellTemplate;
+
+        public static readonly DirectProperty<DataGridTemplateColumn, IDataTemplate> CellEditingTemplateProperty =
+                AvaloniaProperty.RegisterDirect<DataGridTemplateColumn, IDataTemplate>(
+                    nameof(CellEditingTemplate),
+                    o => o.CellEditingTemplate,
+                    (o, v) => o.CellEditingTemplate = v);
+
+        public IDataTemplate CellEditingTemplate
+        {
+            get => _cellEditingCellTemplate;
+            set => SetAndRaise(CellEditingTemplateProperty, ref _cellEditingCellTemplate, value);
+        }
+        
         private void OnCellTemplateChanged(AvaloniaPropertyChangedEventArgs e)
         {
             var oldValue = (IDataTemplate)e.OldValue;
@@ -38,7 +52,7 @@ namespace Avalonia.Controls
 
         public DataGridTemplateColumn()
         {
-            IsReadOnly = true;
+            // IsReadOnly = true;
         }
 
         protected override IControl GenerateElement(DataGridCell cell, object dataItem)
@@ -60,7 +74,18 @@ namespace Avalonia.Controls
         protected override IControl GenerateEditingElement(DataGridCell cell, object dataItem, out ICellEditBinding binding)
         {
             binding = null;
-            return GenerateElement(cell, dataItem);
+            if(CellEditingTemplate != null)
+            {
+                return CellEditingTemplate.Build(dataItem);
+            }
+            if (Design.IsDesignMode)
+            {
+                return null;
+            }
+            else
+            {
+                throw DataGridError.DataGridTemplateColumn.MissingTemplateForType(typeof(DataGridTemplateColumn));
+            }
         }
 
         protected override object PrepareCellForEdit(IControl editingElement, RoutedEventArgs editingEventArgs)
@@ -70,7 +95,8 @@ namespace Avalonia.Controls
 
         protected internal override void RefreshCellContent(IControl element, string propertyName)
         {
-            if(propertyName == nameof(CellTemplate) && element.Parent is DataGridCell cell)
+            var cell = element.Parent as DataGridCell;
+            if(propertyName == nameof(CellTemplate) && cell is not null)
             {
                 cell.Content = GenerateElement(cell, cell.DataContext);
             }

From 66a02a37d09b226127b3d7636e18f0d84fbd0f02 Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Tue, 4 Jan 2022 17:27:28 +0100
Subject: [PATCH 2/6] Handle IsReadOnly correct for DataGridTemplateColumn

---
 .../DataGridColumn.cs                         |  2 +-
 .../DataGridTemplateColumn.cs                 | 25 +++++++++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGridColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
index 6b515503aa..8501ce3896 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
@@ -448,7 +448,7 @@ namespace Avalonia.Controls
             internal set;
         }
 
-        public bool IsReadOnly
+        public virtual bool IsReadOnly
         {
             get
             {
diff --git a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
index fbdad0a8ad..e8ccb7df34 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
@@ -15,7 +15,7 @@ namespace Avalonia.Controls
 {
     public class DataGridTemplateColumn : DataGridColumn
     {
-        IDataTemplate _cellTemplate;
+        private IDataTemplate _cellTemplate;
 
         public static readonly DirectProperty<DataGridTemplateColumn, IDataTemplate> CellTemplateProperty =
             AvaloniaProperty.RegisterDirect<DataGridTemplateColumn, IDataTemplate>(
@@ -54,7 +54,7 @@ namespace Avalonia.Controls
         {
             // IsReadOnly = true;
         }
-
+        
         protected override IControl GenerateElement(DataGridCell cell, object dataItem)
         {
             if(CellTemplate != null)
@@ -78,6 +78,10 @@ namespace Avalonia.Controls
             {
                 return CellEditingTemplate.Build(dataItem);
             }
+            else if (CellTemplate != null)
+            {
+                return CellTemplate.Build(dataItem);
+            }
             if (Design.IsDesignMode)
             {
                 return null;
@@ -103,5 +107,22 @@ namespace Avalonia.Controls
 
             base.RefreshCellContent(element, propertyName);
         }
+        
+        public override bool IsReadOnly
+        {
+            get
+            {
+                if (CellEditingTemplate is null)
+                {
+                    return true;
+                }
+
+                return base.IsReadOnly;
+            }
+            set
+            {
+                base.IsReadOnly = value;
+            }
+        }
     }
 }

From cf6c0991f8f52bcd683328dafa011550df184698 Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Tue, 4 Jan 2022 17:27:57 +0100
Subject: [PATCH 3/6] Update Demo

---
 samples/ControlCatalog/Models/Person.cs           | 15 +++++++++++++++
 samples/ControlCatalog/Pages/DataGridPage.xaml    | 12 ++++++++++++
 samples/ControlCatalog/Pages/DataGridPage.xaml.cs |  6 +++---
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/samples/ControlCatalog/Models/Person.cs b/samples/ControlCatalog/Models/Person.cs
index 47f41bc584..cd70fa3959 100644
--- a/samples/ControlCatalog/Models/Person.cs
+++ b/samples/ControlCatalog/Models/Person.cs
@@ -16,6 +16,7 @@ namespace ControlCatalog.Models
         string _firstName;
         string _lastName;
         bool _isBanned;
+        private int _age;
 
         public string FirstName
         {
@@ -59,6 +60,20 @@ namespace ControlCatalog.Models
             }
         }
 
+        
+        /// <summary>
+        ///    Gets or sets the age of the person
+        /// </summary>
+        public int Age
+        {
+            get => _age;
+            set
+            {
+                _age = value;
+                OnPropertyChanged(nameof(Age));
+            }
+        }
+
         Dictionary<string, List<string>> _errorLookup = new Dictionary<string, List<string>>();
 
         void SetError(string propertyName, string error)
diff --git a/samples/ControlCatalog/Pages/DataGridPage.xaml b/samples/ControlCatalog/Pages/DataGridPage.xaml
index 63e873d9b5..451a774cb4 100644
--- a/samples/ControlCatalog/Pages/DataGridPage.xaml
+++ b/samples/ControlCatalog/Pages/DataGridPage.xaml
@@ -64,6 +64,18 @@
               <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridTextColumn Header="Last" Binding="{Binding LastName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridCheckBoxColumn Header="Is Banned" Binding="{Binding IsBanned}" Width="*" IsThreeState="{Binding #IsThreeStateCheckBox.IsChecked, Mode=OneWay}" />
+              <DataGridTemplateColumn Header="Age" >
+                <DataGridTemplateColumn.CellTemplate>
+                  <DataTemplate DataType="local:Person">
+                    <TextBlock Text="{Binding Age, StringFormat='{}{0} years'}" VerticalAlignment="Center" HorizontalAlignment="Center" />
+                  </DataTemplate>
+                </DataGridTemplateColumn.CellTemplate>
+                <DataGridTemplateColumn.CellEditingTemplate>
+                  <DataTemplate DataType="local:Person">
+                    <NumericUpDown Value="{Binding Age}" FormatString="N0" HorizontalAlignment="Stretch" Minimum="0" Maximum="120" />
+                  </DataTemplate>
+                </DataGridTemplateColumn.CellEditingTemplate>
+              </DataGridTemplateColumn>
             </DataGrid.Columns>
           </DataGrid>
           <Button Grid.Row="1" Name="btnAdd" Margin="12,0,12,12" Content="Add" HorizontalAlignment="Right" />
diff --git a/samples/ControlCatalog/Pages/DataGridPage.xaml.cs b/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
index dc5cc49a90..ec2c6651de 100644
--- a/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
@@ -48,9 +48,9 @@ namespace ControlCatalog.Pages
 
             var items = new List<Person>
             {
-                new Person { FirstName = "John", LastName = "Doe" },
-                new Person { FirstName = "Elizabeth", LastName = "Thomas", IsBanned = true },
-                new Person { FirstName = "Zack", LastName = "Ward" }
+                new Person { FirstName = "John", LastName = "Doe" , Age = 30},
+                new Person { FirstName = "Elizabeth", LastName = "Thomas", IsBanned = true , Age = 40 },
+                new Person { FirstName = "Zack", LastName = "Ward" , Age = 50 }
             };
             var collectionView3 = new DataGridCollectionView(items);
 

From 61fd2318faef61e15a6583d3f85e140f7df5defc Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Wed, 5 Jan 2022 11:16:09 +0100
Subject: [PATCH 4/6] Remove unused Constructor

The constructor was needed to override IsReadonly. This is not needed anymore.
---
 src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
index e8ccb7df34..e2245628f2 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
@@ -1,4 +1,4 @@
-// (c) Copyright Microsoft Corporation.
+// (c) Copyright Microsoft Corporation.
 // This source is subject to the Microsoft Public License (Ms-PL).
 // Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
 // All other rights reserved.
@@ -50,11 +50,6 @@ namespace Avalonia.Controls
             var value = (IDataTemplate)e.NewValue;
         }
 
-        public DataGridTemplateColumn()
-        {
-            // IsReadOnly = true;
-        }
-        
         protected override IControl GenerateElement(DataGridCell cell, object dataItem)
         {
             if(CellTemplate != null)

From d21c3cce1ef1a38037d589aad9d126a36b17df11 Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Wed, 5 Jan 2022 11:17:38 +0100
Subject: [PATCH 5/6] Improve Demo

- Set the focus to the TextBox of the NumericUpDown
---
 samples/ControlCatalog/Pages/DataGridPage.xaml   |  2 +-
 .../ControlCatalog/Pages/DataGridPage.xaml.cs    | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/Pages/DataGridPage.xaml b/samples/ControlCatalog/Pages/DataGridPage.xaml
index 451a774cb4..f7e3cf2441 100644
--- a/samples/ControlCatalog/Pages/DataGridPage.xaml
+++ b/samples/ControlCatalog/Pages/DataGridPage.xaml
@@ -72,7 +72,7 @@
                 </DataGridTemplateColumn.CellTemplate>
                 <DataGridTemplateColumn.CellEditingTemplate>
                   <DataTemplate DataType="local:Person">
-                    <NumericUpDown Value="{Binding Age}" FormatString="N0" HorizontalAlignment="Stretch" Minimum="0" Maximum="120" />
+                    <NumericUpDown Value="{Binding Age}" FormatString="N0" HorizontalAlignment="Stretch" Minimum="0" Maximum="120" TemplateApplied="NumericUpDown_OnTemplateApplied" />
                   </DataTemplate>
                 </DataGridTemplateColumn.CellEditingTemplate>
               </DataGridTemplateColumn>
diff --git a/samples/ControlCatalog/Pages/DataGridPage.xaml.cs b/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
index ec2c6651de..c010d38eac 100644
--- a/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DataGridPage.xaml.cs
@@ -6,7 +6,9 @@ using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
 using ControlCatalog.Models;
 using Avalonia.Collections;
+using Avalonia.Controls.Primitives;
 using Avalonia.Data;
+using Avalonia.Threading;
 
 namespace ControlCatalog.Pages
 {
@@ -84,5 +86,19 @@ namespace ControlCatalog.Pages
                 return Comparer.Default.Compare(x, y);
             }
         }
+
+        private void NumericUpDown_OnTemplateApplied(object sender, TemplateAppliedEventArgs e)
+        {
+            // We want to focus the TextBox of the NumericUpDown. To do so we search for this control when the template
+            // is applied, but we postpone the action until the control is actually loaded. 
+            if (e.NameScope.Find<TextBox>("PART_TextBox") is {} textBox)
+            {
+                Dispatcher.UIThread.InvokeAsync(() =>
+                {
+                    textBox.Focus();
+                    textBox.SelectAll();
+                }, DispatcherPriority.Loaded);
+            }
+        }
     }
 }

From 43903f667199a65b4c696e295976945372bb02b2 Mon Sep 17 00:00:00 2001
From: Tim U <tim.uniewki@gmail.com>
Date: Wed, 5 Jan 2022 11:35:39 +0100
Subject: [PATCH 6/6] Insert XML-Comments

---
 .../DataGridTemplateColumn.cs                        | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
index e2245628f2..0e754d5815 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
@@ -32,12 +32,24 @@ namespace Avalonia.Controls
 
         private IDataTemplate _cellEditingCellTemplate;
 
+        /// <summary>
+        /// Defines the <see cref="CellEditingTemplate"/> property.
+        /// </summary>
         public static readonly DirectProperty<DataGridTemplateColumn, IDataTemplate> CellEditingTemplateProperty =
                 AvaloniaProperty.RegisterDirect<DataGridTemplateColumn, IDataTemplate>(
                     nameof(CellEditingTemplate),
                     o => o.CellEditingTemplate,
                     (o, v) => o.CellEditingTemplate = v);
 
+        /// <summary>
+        /// Gets or sets the <see cref="IDataTemplate"/> which is used for the editing mode of the current <see cref="DataGridCell"/>
+        /// </summary>
+        /// <value>
+        /// An <see cref="IDataTemplate"/> for the editing mode of the current <see cref="DataGridCell"/>
+        /// </value>
+        /// <remarks>
+        /// If this property is <see langword="null"/> the column is read-only.
+        /// </remarks>
         public IDataTemplate CellEditingTemplate
         {
             get => _cellEditingCellTemplate;