From 12d7ff1bfc6296f79c0f8bfb03e8959a7900ce87 Mon Sep 17 00:00:00 2001
From: dpse <dpse@users.noreply.github.com>
Date: Wed, 17 Dec 2025 01:45:40 +0100
Subject: [PATCH] Apply NumberFormat changes to NumericUpDown (#20248)

* Add NumericUpDown NumberFormat failing test

* Force text update when NumberFormat has changed

---------

Co-authored-by: Julien Lebosquain <julien@lebosquain.net>
---
 .../NumericUpDown/NumericUpDown.cs            |  2 +-
 .../NumericUpDownTests.cs                     | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs b/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
index d9cc92f0e6..188497d230 100644
--- a/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
+++ b/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
@@ -450,7 +450,7 @@ namespace Avalonia.Controls
         {
             if (IsInitialized)
             {
-                SyncTextAndValueProperties(false, null);
+                SyncTextAndValueProperties(false, null, true);
             }
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/NumericUpDownTests.cs b/tests/Avalonia.Controls.UnitTests/NumericUpDownTests.cs
index f03bd5b633..42e58f4d8d 100644
--- a/tests/Avalonia.Controls.UnitTests/NumericUpDownTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/NumericUpDownTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Reactive.Subjects;
 using Avalonia.Controls.Templates;
@@ -80,6 +81,26 @@ namespace Avalonia.Controls.UnitTests
             });
         }
 
+        [Fact]
+        public void NumberFormat_Is_Applied_Immediately()
+        {
+            RunTest((control, textbox) =>
+            {
+                const decimal value = 10.11m;
+                var initialNumberFormat = new NumberFormatInfo { NumberDecimalSeparator = "." };
+                var newNumberFormat = new NumberFormatInfo { NumberDecimalSeparator = ";" };
+
+                // Establish and verify initial conditions.
+                control.NumberFormat = initialNumberFormat;
+                control.Value = value;
+                Assert.Equal(value.ToString(initialNumberFormat), control.Text);
+
+                // Check that NumberFormat is applied.
+                control.NumberFormat = newNumberFormat;
+                Assert.Equal(value.ToString(newNumberFormat), control.Text);
+            });
+        }
+
         public static IEnumerable<object[]> Increment_Decrement_TestData()
         {
             // if min and max are not defined and value was null, 0 should be ne new value after spin