From 8a7f6cd4e77e3086ff23ac075e1634b9139bd160 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=BCnther=20Wimpassinger?=
 <guenther.wimpassinger@smartpoint.at>
Date: Sun, 28 Sep 2025 03:12:13 +0200
Subject: [PATCH] Constants use the CultureInfo from the CsvConfiguration if
 provided.

---
 .../Expressions/ObjectRecordWriter.cs         | 10 +-
 .../CsvHelper.Tests/Writing/ConstantTests.cs  | 98 ++++++++++++++++++-
 2 files changed, 106 insertions(+), 2 deletions(-)

diff --git a/src/CsvHelper/Expressions/ObjectRecordWriter.cs b/src/CsvHelper/Expressions/ObjectRecordWriter.cs
index e00119024..027f347e3 100644
--- a/src/CsvHelper/Expressions/ObjectRecordWriter.cs
+++ b/src/CsvHelper/Expressions/ObjectRecordWriter.cs
@@ -80,6 +80,11 @@ protected override Action<T> CreateWriteDelegate<T>(Type type)
 				{
 					fieldExpression = Expression.Constant(memberMap.Data.Constant);
 					var typeConverterExpression = Expression.Constant(Writer.Context.TypeConverterCache.GetConverter(memberMap.Data.Constant.GetType()));
+
+					memberMap.Data.TypeConverterOptions = TypeConverterOptions.Merge(
+						new TypeConverterOptions { CultureInfo = Writer.Configuration.CultureInfo },
+						memberMap.Data.TypeConverterOptions);
+
 					var method = typeof(ITypeConverter).GetMethod(nameof(ITypeConverter.ConvertToString))!;
 					fieldExpression = Expression.Convert(fieldExpression, typeof(object));
 					fieldExpression = Expression.Call(typeConverterExpression, method, fieldExpression, Expression.Constant(Writer), Expression.Constant(memberMap.Data));
@@ -96,7 +101,10 @@ protected override Action<T> CreateWriteDelegate<T>(Type type)
 				fieldExpression = ExpressionManager.CreateGetMemberExpression(recordParameterConverted, Writer.Context.Maps[type]!, memberMap)!;
 
 				var typeConverterExpression = Expression.Constant(memberMap.Data.TypeConverter);
-				memberMap.Data.TypeConverterOptions = TypeConverterOptions.Merge(new TypeConverterOptions { CultureInfo = Writer.Configuration.CultureInfo }, Writer.Context.TypeConverterOptionsCache.GetOptions(memberMap.Data.Member!.MemberType()), memberMap.Data.TypeConverterOptions);
+				memberMap.Data.TypeConverterOptions = TypeConverterOptions.Merge(
+					new TypeConverterOptions { CultureInfo = Writer.Configuration.CultureInfo },
+					Writer.Context.TypeConverterOptionsCache.GetOptions(memberMap.Data.Member!.MemberType()),
+					memberMap.Data.TypeConverterOptions);
 
 				var method = typeof(ITypeConverter).GetMethod(nameof(ITypeConverter.ConvertToString))!;
 				fieldExpression = Expression.Convert(fieldExpression, typeof(object));
diff --git a/tests/CsvHelper.Tests/Writing/ConstantTests.cs b/tests/CsvHelper.Tests/Writing/ConstantTests.cs
index cc8087211..be218939b 100644
--- a/tests/CsvHelper.Tests/Writing/ConstantTests.cs
+++ b/tests/CsvHelper.Tests/Writing/ConstantTests.cs
@@ -11,7 +11,7 @@
 
 namespace CsvHelper.Tests.Writing
 {
-	
+
 	public class ConstantTests
 	{
 		[Fact]
@@ -90,6 +90,79 @@ public void IntConstantTest()
 			}
 		}
 
+		[Fact]
+		public void DoubleConstantTest_CultureInvariant()
+		{
+			CultureInfo.CurrentCulture = CultureInfo.InvariantCulture;
+			var config = new CsvConfiguration(CultureInfo.InvariantCulture)
+			{
+				HasHeaderRecord = false,
+			};
+			using (var writer = new StringWriter())
+			using (var csv = new CsvWriter(writer, config))
+			{
+				var records = new List<Test>
+				{
+					new Test { Id = 1, Name = "one" },
+				};
+
+				csv.Context.RegisterClassMap<TestDoubleMap>();
+				csv.WriteRecords(records);
+				writer.Flush();
+
+				Assert.Equal("3.141592,3.1415\r\n", writer.ToString());
+			}
+		}
+
+		[Fact]
+		public void DoubleConstantTest_CultureDe()
+		{
+			CultureInfo.CurrentCulture = CultureInfo.InvariantCulture;
+			var config = new CsvConfiguration(new CultureInfo("de-DE"))
+			{
+				HasHeaderRecord = false,
+			};
+			using (var writer = new StringWriter())
+			using (var csv = new CsvWriter(writer, config))
+			{
+				var records = new List<Test>
+				{
+					new Test { Id = 1, Name = "one" },
+				};
+
+				csv.Context.RegisterClassMap<TestDoubleMap>();
+				csv.WriteRecords(records);
+				writer.Flush();
+
+				Assert.Equal("3,141592;3,1415\r\n", writer.ToString());
+			}
+		}
+
+		[Fact]
+		public void DoubleConstantTest_CultureDeOverrideInvariant()
+		{
+			CultureInfo.CurrentCulture = CultureInfo.InvariantCulture;
+			var config = new CsvConfiguration(new CultureInfo("de-DE"))
+			{
+				HasHeaderRecord = false,
+			};
+			using (var writer = new StringWriter())
+			using (var csv = new CsvWriter(writer, config))
+			{
+				var records = new List<Test>
+				{
+					new Test { Id = 1, Name = "one" },
+				};
+
+				csv.Context.RegisterClassMap(new TestDoublCultureOverrideMap(CultureInfo.InvariantCulture));
+				csv.WriteRecords(records);
+				writer.Flush();
+
+				Assert.Equal("3,141592;3.1415\r\n", writer.ToString());
+			}
+		}
+
+
 		private class Test
 		{
 			public int Id { get; set; }
@@ -122,5 +195,28 @@ public TestStringMap()
 				Map(m => m.Name).Constant("constant");
 			}
 		}
+
+		private sealed class TestDoubleMap : ClassMap<Test>
+		{
+			public TestDoubleMap()
+			{
+				Map(m => m.Id).Ignore();
+				Map(m => m.Name).Ignore();
+				Map().Constant(3.141592);
+				Map().Constant(3.1415m);
+			}
+		}
+
+		private sealed class TestDoublCultureOverrideMap : ClassMap<Test>
+		{
+			public TestDoublCultureOverrideMap(CultureInfo culture)
+			{
+				Map(m => m.Id).Ignore();
+				Map(m => m.Name).Ignore();
+				Map().Constant(3.141592);
+				Map().Constant(3.1415m).TypeConverterOption.CultureInfo(culture);
+			}
+		}
+
 	}
 }