From 0ff7d5da9788321263f47f1e6f354d96af9690e7 Mon Sep 17 00:00:00 2001
From: Joris Voermans <joris@clevr.net>
Date: Mon, 13 Jan 2025 08:51:16 +0100
Subject: [PATCH] TextBoxLineCountBehavior: Fixed issue with
 UpdateAttachedProperties being called after detached causing
 NullReferenceException (#3769)

---
 .../Behaviors/TextBoxLineCountBehavior.cs                  | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/MaterialDesignThemes.Wpf/Behaviors/TextBoxLineCountBehavior.cs b/src/MaterialDesignThemes.Wpf/Behaviors/TextBoxLineCountBehavior.cs
index 7940b4e1a6..582294a800 100644
--- a/src/MaterialDesignThemes.Wpf/Behaviors/TextBoxLineCountBehavior.cs
+++ b/src/MaterialDesignThemes.Wpf/Behaviors/TextBoxLineCountBehavior.cs
@@ -12,8 +12,11 @@ public class TextBoxLineCountBehavior : Behavior<TextBox>
 
     private void UpdateAttachedProperties()
     {
-        AssociatedObject.SetCurrentValue(TextFieldAssist.TextBoxLineCountProperty, AssociatedObject.LineCount);
-        AssociatedObject.SetCurrentValue(TextFieldAssist.TextBoxIsMultiLineProperty, AssociatedObject.LineCount > 1);
+        if (AssociatedObject != null)
+        {
+            AssociatedObject.SetCurrentValue(TextFieldAssist.TextBoxLineCountProperty, AssociatedObject.LineCount);
+            AssociatedObject.SetCurrentValue(TextFieldAssist.TextBoxIsMultiLineProperty, AssociatedObject.LineCount > 1);
+        }
     }
 
     protected override void OnAttached()