From 952847778c3346091fb318f994e54afff5a2981c Mon Sep 17 00:00:00 2001
From: Johan Appelgren <johan.appelgren@gmail.com>
Date: Tue, 23 Apr 2024 23:28:08 +0200
Subject: [PATCH] Don't rely on VisibleColumnCount since it is updated later.

---
 .../Primitives/DataGridColumnHeadersPresenter.cs   | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls.DataGrid/Primitives/DataGridColumnHeadersPresenter.cs b/src/Avalonia.Controls.DataGrid/Primitives/DataGridColumnHeadersPresenter.cs
index 0ff364bf5e8..e74a91930f8 100644
--- a/src/Avalonia.Controls.DataGrid/Primitives/DataGridColumnHeadersPresenter.cs
+++ b/src/Avalonia.Controls.DataGrid/Primitives/DataGridColumnHeadersPresenter.cs
@@ -124,7 +124,19 @@ int IChildIndexProvider.GetChildIndex(ILogical child)
 
         bool IChildIndexProvider.TryGetTotalCount(out int count)
         {
-            count = OwningGrid.ColumnsInternal.VisibleColumnCount;
+            // VisibleColumnCount is updated the next measure pass after columns are added or removed
+            // but this is called as the column is being added or removed. 
+            // count = OwningGrid.ColumnsInternal.VisibleColumnCount;
+
+            count = 0;
+            for (int i = 0; i < Children.Count; i++)
+            {
+                if (Children[i] is DataGridColumnHeader { OwningColumn: { IsVisible: true } and not DataGridFillerColumn })
+                {
+                    count++;
+                }
+            }
+
             return true;
         }