Merge pull request #7094 from timunie/fix/DataGridHeaderToBeStyledProperty

fix: Make DataGridColumn.Header and .HeaderTemplate a DirectProperty

src/Avalonia.Controls.DataGrid/DataGridColumn.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.
@@ -400,45 +400,40 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        ///    Backing field for Header property
+        /// </summary>
+        public static readonly DirectProperty<DataGridColumn, object> HeaderProperty =
+            AvaloniaProperty.RegisterDirect<DataGridColumn, object>(
+                nameof(Header),
+                o => o.Header,
+                (o, v) => o.Header = v);
+
+        /// <summary>
+        ///    Gets or sets the <see cref="DataGridColumnHeader"/> content 
+        /// </summary>
         public object Header
         {
-            get
-            {
-                return _header;
-            }
-            set
-            {
-                if (_header != value)
-                {
-                    _header = value;
-                    if (_headerCell != null)
-                    {
-                        _headerCell.Content = value;
-                    }
-                }
-            }
+            get { return _header; }
+            set { SetAndRaise(HeaderProperty, ref _header, value); }
         }
+        
+        /// <summary>
+        ///    Backing field for Header property
+        /// </summary>
+        public static readonly DirectProperty<DataGridColumn, IDataTemplate> HeaderTemplateProperty =
+            AvaloniaProperty.RegisterDirect<DataGridColumn, IDataTemplate>(
+                nameof(HeaderTemplate),
+                o => o.HeaderTemplate,
+                (o, v) => o.HeaderTemplate = v);
 
         /// <summary>
         ///  Gets or sets an <see cref="IDataTemplate"/> for the <see cref="Header"/>
         /// </summary>
         public IDataTemplate HeaderTemplate
         {
-            get
-            {
-                return _headerTemplate;
-            }
-            set
-            {
-                if (_headerTemplate != value)
-                {
-                    _headerTemplate = value;
-                    if (_headerCell != null)
-                    {
-                        _headerCell.ContentTemplate = value;
-                    }
-                }
-            }
+            get { return _headerTemplate; }
+            set { SetAndRaise(HeaderTemplateProperty, ref _headerTemplate, value); }
         }
         
         public bool IsAutoGenerated
@@ -874,10 +869,11 @@ namespace Avalonia.Controls
         {
             var result = new DataGridColumnHeader
             {
-                OwningColumn = this,
-                Content = _header,
-                ContentTemplate = _headerTemplate
+                OwningColumn = this
             };
+            result[!ContentControl.ContentProperty] = this[!HeaderProperty];
+            result[!ContentControl.ContentTemplateProperty] = this[!HeaderTemplateProperty];
+            
             //result.EnsureStyle(null);
 
             return result;