Updated the README.md file

README.md

@@ -1 +1,62 @@
 **[View document in Syncfusion .NET MAUI Knowledge Base](https://www.syncfusion.com/kb/13130/how-to-add-expand-or-collapse-icon-in-the-group-header-of-net-maui-listview-sflistview)**
+
+## Sample
+
+```xaml
+<ContentPage.Resources>
+    <ResourceDictionary>
+        <local:BoolToImageConverter x:Key="BoolToImageConverter"/>
+    </ResourceDictionary>
+</ContentPage.Resources>
+
+<ListView:SfListView x:Name="listView"
+                    ItemSize="70" 
+                    GroupHeaderSize="50"
+                    SelectionMode="Single"
+                    IsStickyGroupHeader="True"
+                    ItemsSource="{Binding ContactsInfo}"
+                    AllowGroupExpandCollapse="True">
+
+    <ListView:SfListView.GroupHeaderTemplate>
+        <DataTemplate>
+        <StackLayout Orientation="Horizontal" BackgroundColor="#E4E4E4">
+            <Image Source="{Binding IsExpand, Converter={StaticResource BoolToImageConverter}}" HeightRequest="30" WidthRequest="30" VerticalOptions="Center" Margin="10,0"/>
+        </StackLayout>
+        </DataTemplate>
+    </ListView:SfListView.GroupHeaderTemplate>
+
+    <ListView:SfListView.ItemTemplate>
+        <DataTemplate>
+            <code>
+            . . .
+            . . .
+            <code>
+        </DataTemplate>
+    </ListView:SfListView.ItemTemplate>
+</ListView:SfListView>
+
+C#:
+
+ListView.DataSource.GroupDescriptors.Add(new GroupDescriptor()
+{
+    PropertyName = "ContactName",
+    KeySelector = (object obj1) =>
+    {
+        var item = (obj1 as ListViewContactInfo);
+        return item.ContactName[0].ToString();
+    },
+});
+
+public class BoolToImageConverter : IValueConverter
+{
+    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+    {
+        return (bool)value ? "group_expand.png" : "group_collapse.png";
+    }
+
+    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+    {
+        throw new NotImplementedException();
+    }
+}
+```