Formula attribute added to support in rows with dto or dynamic attrib…

src/MiniExcel/Attributes/ExcelColumnAttribute.cs

@@ -21,6 +21,8 @@ public class ExcelColumnAttribute : Attribute
 
         public bool Ignore { get; set; }
 
+        public ColumnType Type { get; set; } = ColumnType.Value;
+
         public int Index
         {
             get => _index;
@@ -50,6 +52,7 @@ private void Init(int index, string columnName = null)
         }
     }
 
+    public enum ColumnType { Value, Formula }
 
     public class DynamicExcelColumn : ExcelColumnAttribute
     {

src/MiniExcel/OpenXml/Constants/WorksheetXml.cs

@@ -1,4 +1,5 @@
 using System.Globalization;
+using MiniExcelLibs.Attributes;
 
 namespace MiniExcelLibs.OpenXml.Constants
 {
@@ -52,14 +53,13 @@ internal static string Column(int? colIndex, double? columnWidth)
         internal static string EmptyCell(string cellReference, string styleIndex)
             => $"<x:c r=\"{cellReference}\" s=\"{styleIndex}\"></x:c>";
         //t check avoid format error ![image](https://user-images.githubusercontent.com/12729184/118770190-9eee3480-b8b3-11eb-9f5a-87a439f5e320.png)
-        internal static string Cell(string cellReference, string cellType, string styleIndex, string cellValue, bool preserveSpace = false)
-            => $"<x:c r=\"{cellReference}\"{(cellType == null ? string.Empty : $" t=\"{cellType}\"")} s=\"{styleIndex}\"{(preserveSpace ? " xml:space=\"preserve\"" : string.Empty)}><x:v>{cellValue}</x:v></x:c>";
+        internal static string Cell(string cellReference, string cellType, string styleIndex, string cellValue, bool preserveSpace = false, ColumnType columnType = ColumnType.Value)
+            => $"<x:c r=\"{cellReference}\"{(cellType == null ? string.Empty : $" t=\"{cellType}\"")} s=\"{styleIndex}\"{(preserveSpace ? " xml:space=\"preserve\"" : string.Empty)}><x:{(columnType == ColumnType.Formula ? "f" : "v")}>{cellValue}</x:{(columnType == ColumnType.Formula ? "f" : "v")}></x:c>";
 
         internal static string Autofilter(string dimensionRef)
             => $"<x:autoFilter ref=\"{dimensionRef}\" />";
 
         internal static string Drawing(int sheetIndex)
             => $"<x:drawing r:id=\"drawing{sheetIndex}\" />";
-
     }
 }

src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.Async.cs

@@ -1,4 +1,5 @@
-using MiniExcelLibs.OpenXml.Constants;
+using MiniExcelLibs.Attributes;
+using MiniExcelLibs.OpenXml.Constants;
 using MiniExcelLibs.Utils;
 using MiniExcelLibs.Zip;
 using System;
@@ -459,10 +460,11 @@ private async Task WriteCellAsync(MiniExcelAsyncStreamWriter writer, int rowInde
             var styleIndex = tuple.Item1;
             var dataType = tuple.Item2;
             var cellValue = tuple.Item3;
+            var columnType = p.ExcelColumnType;
 
             /*Prefix and suffix blank space will lost after SaveAs #294*/
             var preserveSpace = cellValue != null && (cellValue.StartsWith(" ", StringComparison.Ordinal) || cellValue.EndsWith(" ", StringComparison.Ordinal));
-            await writer.WriteAsync(WorksheetXml.Cell(columnReference, dataType, styleIndex, cellValue, preserveSpace: preserveSpace));
+            await writer.WriteAsync(WorksheetXml.Cell(columnReference, dataType, styleIndex, cellValue, preserveSpace: preserveSpace, columnType: columnType));
         }
 
         private async Task GenerateEndXmlAsync(CancellationToken cancellationToken)

src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.DefaultOpenXml.cs

@@ -103,6 +103,7 @@ private ExcelColumnInfo GetColumnInfosFromDynamicConfiguration(string columnName
 
             prop.Nullable = true;
             prop.ExcelIgnore = dynamicColumn.Ignore;
+            prop.ExcelColumnType = dynamicColumn.Type;
             prop.ExcelColumnIndex = dynamicColumn.Index;
             prop.ExcelColumnWidth = dynamicColumn.Width;
             //prop.ExcludeNullableType = item2[key]?.GetType();

src/MiniExcel/OpenXml/ExcelOpenXmlSheetWriter.cs

@@ -1,4 +1,5 @@
-using MiniExcelLibs.OpenXml.Constants;
+using MiniExcelLibs.Attributes;
+using MiniExcelLibs.OpenXml.Constants;
 using MiniExcelLibs.OpenXml.Models;
 using MiniExcelLibs.Utils;
 using MiniExcelLibs.Zip;
@@ -579,10 +580,11 @@ private void WriteCell(MiniExcelStreamWriter writer, int rowIndex, int cellIndex
             var styleIndex = tuple.Item1; // https://learn.microsoft.com/en-us/dotnet/api/documentformat.openxml.spreadsheet.cell?view=openxml-3.0.1
             var dataType = tuple.Item2; // https://learn.microsoft.com/en-us/dotnet/api/documentformat.openxml.spreadsheet.cellvalues?view=openxml-3.0.1
             var cellValue = tuple.Item3;
+            var columnType = columnInfo?.ExcelColumnType ?? ColumnType.Value;
 
             /*Prefix and suffix blank space will lost after SaveAs #294*/
             var preserveSpace = cellValue != null && (cellValue.StartsWith(" ", StringComparison.Ordinal) || cellValue.EndsWith(" ", StringComparison.Ordinal));
-            writer.Write(WorksheetXml.Cell(columnReference, dataType, styleIndex, cellValue, preserveSpace: preserveSpace));
+            writer.Write(WorksheetXml.Cell(columnReference, dataType, styleIndex, cellValue, preserveSpace: preserveSpace, columnType: columnType));
         }
 
         private static void WriteCell(MiniExcelStreamWriter writer, string cellReference, string columnName)

src/MiniExcel/Utils/CustomPropertyHelper.cs

@@ -24,6 +24,7 @@ internal class ExcelColumnInfo
         public string ExcelIndexName { get; internal set; }
         public bool ExcelIgnore { get; internal set; }
         public int ExcelFormatId { get; internal set; }
+        public ColumnType ExcelColumnType { get; internal set; }
     }
 
     internal class ExcellSheetInfo
@@ -206,7 +207,8 @@ private static IEnumerable<ExcelColumnInfo> ConvertToExcelCustomPropertyInfo(Pro
                     ExcelIndexName = p.GetAttribute<ExcelColumnIndexAttribute>()?.ExcelXName ?? excelColumn?.IndexName,
                     ExcelColumnWidth = p.GetAttribute<ExcelColumnWidthAttribute>()?.ExcelColumnWidth ?? excelColumn?.Width,
                     ExcelFormat = excelFormat ?? excelColumn?.Format,
-                    ExcelFormatId = excelColumn?.FormatId ?? -1
+                    ExcelFormatId = excelColumn?.FormatId ?? -1,
+                    ExcelColumnType = excelColumn?.Type ?? ColumnType.Value
                 };
             }).Where(_ => _ != null);
         }
@@ -307,6 +309,7 @@ internal static void SetDictionaryColumnInfo(List<ExcelColumnInfo> _props, objec
                         p.ExcelColumnName = dynamicColumn.Name;
                     isIgnore = dynamicColumn.Ignore;
                     p.ExcelColumnWidth = dynamicColumn.Width;
+                    p.ExcelColumnType = dynamicColumn.Type;
                 }
             }
             if (!isIgnore)