From 2ce7f52e454df14359ca64d963ed6f1da28aec9e Mon Sep 17 00:00:00 2001
From: Jef Van den Brandt <Jef.VandenBrandt@cheops.be>
Date: Tue, 26 Mar 2024 13:17:20 +0100
Subject: [PATCH] Support writing DateOnly type to Excel

---
 src/MiniExcel/MiniExcelLibs.csproj            |  5 ++++
 .../OpenXml/ExcelOpenXmlSheetWriter.cs        | 23 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/src/MiniExcel/MiniExcelLibs.csproj b/src/MiniExcel/MiniExcelLibs.csproj
index 56ae2a5d..5b1c3733 100644
--- a/src/MiniExcel/MiniExcelLibs.csproj
+++ b/src/MiniExcel/MiniExcelLibs.csproj
@@ -54,4 +54,9 @@ Todo : https://github.com/mini-software/MiniExcel/projects/1?fullscreen=true</De
 	<ItemGroup Condition="'$(GITHUB_ACTIONS)' == 'true'">
 		<PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
 	</ItemGroup>
+	<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+	  <PackageReference Include="Portable.System.DateTimeOnly">
+	    <Version>8.0.0</Version>
+	  </PackageReference>
+	</ItemGroup>
 </Project>
diff --git a/src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs b/src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs
index 7c595d50..2552dc27 100644
--- a/src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs
+++ b/src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs
@@ -574,6 +574,29 @@ private Tuple<string, string, string> GetCellValue(int rowIndex, int cellIndex,
                         cellValue = ((DateTime)value).ToString(columnInfo.ExcelFormat, _configuration.Culture);
                     }
                 }
+#if NETSTANDARD2_0_OR_GREATER
+                else if (type == typeof(DateOnly))
+                {
+                    if (_configuration.Culture != CultureInfo.InvariantCulture)
+                    {
+                        dataType = "str";
+                        cellValue = ((DateOnly)value).ToString(_configuration.Culture);
+                    }
+                    else if (columnInfo == null || columnInfo.ExcelFormat == null)
+                    {
+                        var day = (DateOnly)value;
+                        dataType = "n";
+                        styleIndex = "3";
+                        cellValue = day.ToDateTime(TimeOnly.MinValue).ToOADate().ToString(CultureInfo.InvariantCulture);
+                    }
+                    else
+                    {
+                        // TODO: now it'll lose date type information
+                        dataType = "str";
+                        cellValue = ((DateOnly)value).ToString(columnInfo.ExcelFormat, _configuration.Culture);
+                    }
+                }
+#endif
                 else
                 {
                     //TODO: _configuration.Culture