fixed checking for negative sign when using custom number format. (#2259)

Author: AdrianEPPlus

src/EPPlus/ExcelRangeBase.cs

@@ -816,7 +816,6 @@ public string Text
         {
             get
             {
-
                 object value;
                 if (IsSingleCell || IsName)
                 {

src/EPPlus/Utils/String/ValueToTextHandler.cs

@@ -231,7 +231,12 @@ private static string FormatNumber(double d, string format, CultureInfo cultureI
 
         private static string CheckAndRemoveNegativeSign(string format, string s, string ns)
         {
-            if ((s.StartsWith($"{ns}{ns}") || s.StartsWith($"{ns}-")) && (format.StartsWith(ns) || format.StartsWith("-")))
+            //This regex pattern ^(\[[^\]]+\]|[\\'\""\*_])* removes:
+            //                     \[[^\]]+\] : This part removes Anything inside square brackets
+            //                                [\\'\""\*_] : This part removes Backslashes, quotes, asterisks and underlines
+            string trimmedFormat = System.Text.RegularExpressions.Regex.Replace(format, @"^(\[[^\]]+\]|[\\'\""\*_])*", "");
+            bool formatStartsWithNegative = trimmedFormat.StartsWith(ns) || trimmedFormat.StartsWith("-");
+            if ((s.StartsWith($"{ns}{ns}") || s.StartsWith($"{ns}-")) && formatStartsWithNegative)
             {
                 return s.Remove(1, 1);
             }

src/EPPlusTest/Issues/WorksheetIssues.cs

@@ -1079,5 +1079,17 @@ public void testRepro()
             }
             SwitchBackToCurrentCulture();
         }
+
+        [TestMethod]
+        public void i2258()
+        {
+            var p = OpenTemplatePackage("repro2.xlsx");
+            var ws = p.Workbook.Worksheets.First();
+            var a1 = ws.Cells["A1"].Text;
+            var b1 = ws.Cells["B1"].Text;
+            Assert.AreEqual("-/- 1 000", a1);
+            Assert.AreEqual("-/- 2 000", b1);
+        }
+
     }
 }