Add Property DataGridColumn.HeaderTemplate

samples/ControlCatalog/Pages/DataGridPage.xaml

@@ -4,6 +4,12 @@
              x:Class="ControlCatalog.Pages.DataGridPage">
   <UserControl.Resources>
     <local:GDPValueConverter x:Key="GDPConverter" />
+    <DataTemplate x:Key="Demo.DataTemplates.CountryHeader">
+      <StackPanel Orientation="Horizontal" Spacing="5">
+        <PathIcon Height="12" Data="M 255 116 A 1 1 0 0 0 254 117 L 254 130 A 1 1 0 0 0 255 131 A 1 1 0 0 0 256 130 L 256 123.87109 C 256.1125 123.90694 256.2187 123.94195 256.33984 123.97852 C 257.18636 124.23404 258.19155 124.5 259 124.5 C 259.80845 124.5 260.52133 124.2168 261.17773 123.9668 C 261.83414 123.7168 262.43408 123.5 263 123.5 C 263.56592 123.5 264.5612 123.73404 265.37109 123.97852 C 266.18098 124.22299 266.82227 124.4668 266.82227 124.4668 A 0.50005 0.50005 0 0 0 267.5 124 L 267.5 118 A 0.50005 0.50005 0 0 0 267.17773 117.5332 C 267.17773 117.5332 266.50667 117.27701 265.66016 117.02148 C 264.81364 116.76596 263.80845 116.5 263 116.5 C 262.19155 116.5 261.47867 116.7832 260.82227 117.0332 C 260.16586 117.2832 259.56592 117.5 259 117.5 C 258.43408 117.5 257.4388 117.26596 256.62891 117.02148 C 256.39123 116.94974 256.17716 116.87994 255.98047 116.81445 A 1 1 0 0 0 255 116 z M 263 117.5 C 263.56592 117.5 264.5612 117.73404 265.37109 117.97852 C 266.00097 118.16865 266.29646 118.28239 266.5 118.35742 L 266.5 120.29297 C 266.25708 120.21012 265.97978 120.11797 265.66016 120.02148 C 264.81364 119.76596 263.80845 119.5 263 119.5 C 262.19155 119.5 261.47867 119.7832 260.82227 120.0332 C 260.16586 120.2832 259.56592 120.5 259 120.5 C 258.43408 120.5 257.4388 120.26596 256.62891 120.02148 C 256.39971 119.9523 256.19148 119.88388 256 119.82031 L 256 117.87109 C 256.1125 117.90694 256.2187 117.94195 256.33984 117.97852 C 257.18636 118.23404 258.19155 118.5 259 118.5 C 259.80845 118.5 260.52133 118.2168 261.17773 117.9668 C 261.83414 117.7168 262.43408 117.5 263 117.5 z M 263 120.5 C 263.56592 120.5 264.5612 120.73404 265.37109 120.97852 C 265.8714 121.12954 266.2398 121.25641 266.5 121.34961 L 266.5 123.30469 C 266.22286 123.20649 266.12863 123.1629 265.66016 123.02148 C 264.81364 122.76596 263.80845 122.5 263 122.5 C 262.19155 122.5 261.47867 122.7832 260.82227 123.0332 C 260.16586 123.2832 259.56592 123.5 259 123.5 C 258.43408 123.5 257.4388 123.26596 256.62891 123.02148 C 256.39971 122.9523 256.19148 122.88388 256 122.82031 L 256 120.87109 C 256.1125 120.90694 256.2187 120.94195 256.33984 120.97852 C 257.18636 121.23404 258.19155 121.5 259 121.5 C 259.80845 121.5 260.52133 121.2168 261.17773 120.9668 C 261.83414 120.7168 262.43408 120.5 263 120.5 z" />
+        <TextBlock Text="{Binding}"/>
+      </StackPanel>
+    </DataTemplate>
   </UserControl.Resources>
   <UserControl.Styles>
     <Style Selector="DataGridCell.gdp">
@@ -28,7 +34,8 @@
                     DockPanel.Dock="Top"/>
           <DataGrid Name="dataGrid1" Margin="12" CanUserResizeColumns="True" CanUserReorderColumns="True" CanUserSortColumns="True" HeadersVisibility="All">
             <DataGrid.Columns>
-              <DataGridTextColumn Header="Country" Binding="{Binding Name}" Width="6*" MinWidth="400"  />
+              <!-- Using HeaderTemplate -->
+              <DataGridTextColumn Header="Country" HeaderTemplate="{StaticResource Demo.DataTemplates.CountryHeader}" Binding="{Binding Name}" Width="6*" MinWidth="400" />
               <!-- CompiledBinding example of usage. -->
               <DataGridTextColumn Header="Region" Binding="{CompiledBinding Region}" Width="4*" x:DataType="local:Country" />
               <DataGridTextColumn Header="Population" Binding="{Binding Population}" Width="3*" />

src/Avalonia.Controls.DataGrid/DataGridColumn.cs

@@ -12,6 +12,7 @@ using System;
 using System.ComponentModel;
 using System.Linq;
 using System.Diagnostics;
+using Avalonia.Controls.Templates;
 using Avalonia.Controls.Utils;
 using Avalonia.Markup.Xaml.MarkupExtensions;
 
@@ -29,6 +30,7 @@ namespace Avalonia.Controls
         private bool _settingWidthInternally;
         private int _displayIndexWithFiller;
         private object _header;
+        private IDataTemplate _headerTemplate;
         private DataGridColumnHeader _headerCell;
         private IControl _editingElement;
         private ICellEditBinding _editBinding;
@@ -416,6 +418,28 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <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;
+                    }
+                }
+            }
+        }
+        
         public bool IsAutoGenerated
         {
             get;
@@ -850,7 +874,8 @@ namespace Avalonia.Controls
             var result = new DataGridColumnHeader
             {
                 OwningColumn = this,
-                Content = _header
+                Content = _header,
+                ContentTemplate = _headerTemplate
             };
             //result.EnsureStyle(null);
 

src/Avalonia.Controls.DataGrid/Themes/Default.xaml

@@ -47,7 +47,8 @@
                 HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                 VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                 Margin="{TemplateBinding Padding}">
-            <ContentPresenter Content="{TemplateBinding Content}"/>
+            <ContentPresenter Content="{TemplateBinding Content}" 
+                              ContentTemplate="{TemplateBinding ContentTemplate}" />
 
             <Path Name="SortIcon"
                   Grid.Column="1"

src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml

@@ -193,7 +193,8 @@
                                 Width="Auto" />
             </Grid.ColumnDefinitions>
 
-            <ContentPresenter Content="{TemplateBinding Content}" />
+            <ContentPresenter Content="{TemplateBinding Content}" 
+                              ContentTemplate="{TemplateBinding ContentTemplate}" />
 
             <Path Name="SortIcon"
                   Grid.Column="1"