EPPlusSoftware#779 implemented FullPrecision workbook property

src/EPPlus/ExcelWorkbook.cs

@@ -1096,7 +1096,25 @@ public bool FullCalcOnLoad
  }
  }
 
- ExcelThemeManager _theme = null;
+ private const string FULL_PRECISION = "d:calcPr/@fullPrecision";
+ /// <summary>
+ /// Should Excel calculate with the displayed value?
+ /// </summary>
+ public bool FullPrecision
+ {
+ get
+ {
+
+ return GetXmlNodeBool(FULL_PRECISION, true);
+ }
+ set
+ {
+ SetXmlNodeBool(FULL_PRECISION, value);
+ }
+ }
+
+
+ ExcelThemeManager _theme = null;
  /// <summary>
  /// Create and manage the theme for the workbook.
  /// </summary>

src/EPPlus/ExcelWorksheet.cs

@@ -44,6 +44,7 @@
 using OfficeOpenXml.Sorting;
 using OfficeOpenXml.Constants;
 using OfficeOpenXml.Drawing.Interfaces;
+using OfficeOpenXml.FormulaParsing.Utilities;
 using OfficeOpenXml.Packaging;
 namespace OfficeOpenXml
 {
@@ -4203,8 +4204,65 @@ internal int GetStyleInner(int row, int col)
  /// <param name="value">value</param>
  internal void SetValueInner(int row, int col, object value)
  {
- _values.SetValue_Value(row, col, value);
+ if (!value.IsNumeric()
+ || Workbook.FullPrecision)
+ {
+ _values.SetValue_Value(row, col, value);
+ return;
+ }
+
+ byte? numberOfDecimals = GetNumberOfDecimals(Cells[row, col]);
+
+ _values.SetValue_Value(row, col, 
+ RoundValue(value, numberOfDecimals));
  }
+
+ private const string _DECIMAL_PLACES_PATTERN = @"\.(?<dec> [#0]+ )";
+ private static byte? GetNumberOfDecimals(IExcelCell cell)
+ {
+ var formatting = cell.Style.Numberformat.Format;
+
+ if (string.IsNullOrEmpty(formatting))
+ return null;
+
+ // get number of decimal places #.# or 0.00
+ var match = Regex.Match(formatting, _DECIMAL_PLACES_PATTERN,
+ RegexOptions.IgnorePatternWhitespace);
+
+ if (match.Success)
+ {
+ if (!string.IsNullOrEmpty(match.Groups["dec"].Value))
+ return (byte)match.Groups["dec"].Value.Length;
+ }
+
+ return 0;
+ }
+
+ private static object RoundValue(object value, byte? numberOfDecimals)
+ {
+ if (numberOfDecimals.HasValue
+ && TryParseToDecimal(value, out var val))
+ {
+ return Math.Round(val, numberOfDecimals.Value);
+ }
+
+ return value;
+ }
+
+ private static bool TryParseToDecimal(object number, out decimal val)
+ {
+ if (decimal.TryParse(number.ToString(), out val))
+ return true;
+
+ if (double.TryParse(number.ToString(), out var dblVal))
+ {
+ val = (decimal)dblVal;
+ return true;
+ }
+
+ return false;
+ }
+
  /// <summary>
  /// Set accessor of sheet styleId
  /// </summary>

src/EPPlusTest/Issues.cs

@@ -3965,5 +3965,33 @@ public void i762()
  SaveAndCleanup(p);
  }
  }
+
+ [TestMethod]
+ public void If_full_precision_is_off_value_should_be_calculated_as_seen_issue_779()
+ {
+ //Issue: If Excel has rounding errors(due to the fact that calculation is always
+ //done with floating points) some formulas like "If" are wrong due to aftereffects.
+ //One can do work around that issue by ticking the checkbox "precision as displayed" 
+ //in the advanced excel options.This function was not yet implemented in EPPlus.
+
+ using var p = new ExcelPackage();
+ p.Workbook.Worksheets.Add("first");
+ p.Workbook.FullPrecision = false;
+
+ var sheet = p.Workbook.Worksheets.First();
+
+ sheet.Cells["A1"].Value = 0.0000001;
+ sheet.Cells["A2"].Value = 0.00000001;
+ sheet.Cells["A3"].Formula = "=SUM(A1:A2)";
+ sheet.Cells["A3"].Style.Numberformat.Format = "#,##0";
+ sheet.Cells["A4"].Formula = "=IF(A3=0;\"OK\";\"Not OK\")";
+
+ //var path = Path.Combine(GetLocalResourcesPath(), "FullPrecisionIF.xlsx");
+ //using var p = new ExcelPackage(path);
+
+ p.Workbook.Calculate();
+ Assert.IsFalse(p.Workbook.FullPrecision);
+ Assert.AreEqual("OK", p.Workbook.Worksheets.First().Cells["A4"].Value);
+ }
  }
 }