Format filter query values with invariant culture

src/ParquetViewer.Tests/HelperTests.cs

@@ -285,6 +285,46 @@ public void FloatScientificNotation_IsWrappedInQuotes()
             Assert.AreEqual("Value = '1.23E+20'", query);
         }
 
+        [TestMethod]
+        [DataRow("de-DE")] //comma decimal separator
+        [DataRow("fr-FR")] //comma decimal separator + narrow no-break group separator
+        [DataRow("th-TH")] //non-Gregorian calendar by default
+        public void NumericAndDateFilters_AreCultureInvariant(string cultureName)
+        {
+            //DataView.RowFilter always expects '.' as the decimal separator and a Gregorian date,
+            //regardless of the user's locale. Without invariant formatting, a culture that uses ','
+            //would corrupt the filter since ',' also separates values inside an `IN (...)` clause.
+            var originalCulture = CultureInfo.CurrentCulture;
+            try
+            {
+                CultureInfo.CurrentCulture = new CultureInfo(cultureName);
+
+                Assert.AreEqual("Value = 1.5", ParquetGridView.GenerateFilterQuery(new()
+                {
+                    ("Value", typeof(double), new object[] { 1.5d })
+                }));
+
+                Assert.AreEqual("Value = '1.23E+20'", ParquetGridView.GenerateFilterQuery(new()
+                {
+                    ("Value", typeof(double), new object[] { 1.23e20 })
+                }));
+
+                Assert.AreEqual("Value IN (1.5,2.5)", ParquetGridView.GenerateFilterQuery(new()
+                {
+                    ("Value", typeof(double), new object[] { 1.5d, 2.5d })
+                }));
+
+                Assert.AreEqual("Value = #2024-01-31 13:45:30#", ParquetGridView.GenerateFilterQuery(new()
+                {
+                    ("Value", typeof(DateTime), new object[] { new DateTime(2024, 1, 31, 13, 45, 30) })
+                }));
+            }
+            finally
+            {
+                CultureInfo.CurrentCulture = originalCulture;
+            }
+        }
+
         [TestMethod]
         public void ByteArrayValue_IsCorrectlyTruncated()
         {

src/ParquetViewer/Controls/ParquetGridView.cs

@@ -7,6 +7,7 @@
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
+using System.Globalization;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Text;
@@ -1050,12 +1051,18 @@ public static string GenerateFilterQuery(List<(string ColumnName, Type ValueType
                     {
                         if (valueType == typeof(DateTime))
                         {
-                            //Use a standard date format so the query is always syntactically correct
-                            queryBuilder.AppendFormat(dateValueEscapeFormat, ((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss.FFFFFFF"));
+                            //Use a standard date format so the query is always syntactically correct.
+                            //Invariant culture is required: custom format strings still resolve the calendar from
+                            //the current culture, so locales like th-TH would emit a non-Gregorian year.
+                            queryBuilder.AppendFormat(CultureInfo.InvariantCulture, dateValueEscapeFormat,
+                                ((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss.FFFFFFF", CultureInfo.InvariantCulture));
                         }
                         else if (valueType.IsNumber())
                         {
-                            var stringValue = value.ToString();
+                            //DataView.RowFilter syntax is culture invariant: it always expects '.' as the decimal
+                            //separator. Formatting with the current culture would emit ',' in locales like de-DE,
+                            //which silently corrupts the filter since ',' separates values inside an `IN (...)` clause.
+                            var stringValue = Convert.ToString(value, CultureInfo.InvariantCulture);
                             if ((valueType == typeof(float) || valueType == typeof(double))
                                 && stringValue?.Contains('E', StringComparison.OrdinalIgnoreCase) == true)
                                 stringValue = $"'{stringValue}'"; //scientific notation values need to be wrapped in single quotes