Opening excel file gives message box “content recovery of the work

While I'm trying to open excel file a message box is prompting like "We found a problem with some content in file name. Do you want us to try to recover as much as we can? If you trust the source of this workbook, click Yes.". I don't understand why this happened and none of the internet solution is not working for me. Can anyone help me?

public static string OpenXML(string FolderPath, DataSet tableSet)
{
WorkbookPart wBookPart = null;
var datetime = DateTime.Now.ToString().Replace("/", "_").Replace(":", "_");
string FilePath = "";
foreach (DataTable table1 in tableSet.Tables)
{
if (table1.Rows.Count != 0)
{
using (SpreadsheetDocument spreadsheetDoc = SpreadsheetDocument.Create(FilePath, SpreadsheetDocumentType.Workbook))
{
wBookPart = spreadsheetDoc.AddWorkbookPart();
wBookPart.Workbook = new Workbook();
uint sheetId = 1;
spreadsheetDoc.WorkbookPart.Workbook.Sheets = new Sheets();
Sheets sheets = spreadsheetDoc.WorkbookPart.Workbook.GetFirstChild();
WorkbookStylesPart wbsp = wBookPart.AddNewPart();
wbsp.Stylesheet = CreateStylesheet();
wbsp.Stylesheet.Save();
foreach (DataTable table in tableSet.Tables)
{
if (table.Rows.Count != 0)
{
table.TableName = table.Rows[0]["LeaseCondition"].ToString();
WorksheetPart wSheetPart = wBookPart.AddNewPart();
Sheet sheet = new Sheet() { Id = spreadsheetDoc.WorkbookPart.GetIdOfPart(wSheetPart), SheetId = sheetId, Name = table.TableName };
sheets.Append(sheet);
SheetData sheetData = new SheetData();
wSheetPart.Worksheet = new Worksheet();
Row headerRow = new Row();
Columns columns = new Columns();
int ColumnNumber = 1;
foreach (DataColumn column in table.Columns)
{
Cell cell = new Cell();
cell.DataType = CellValues.String;
cell.CellValue = new CellValue(column.ColumnName);
cell.StyleIndex = 2;
headerRow.AppendChild(cell);
Column column1 = new Column();
column1.Width = 30; ;
column1.BestFit = true;
column1.CustomWidth = true;
column1.Min = Convert.ToUInt32(ColumnNumber);
column1.Max = Convert.ToUInt32(ColumnNumber);
columns.AppendChild(column1);
ColumnNumber = ColumnNumber + 1;
}
wSheetPart.Worksheet.AppendChild(columns);
sheetData.AppendChild(headerRow);
foreach (DataRow dr in table.Rows)
{
Row row = new Row();
foreach (DataColumn column in table.Columns)
{
Cell cell = new Cell();
cell.DataType = CellValues.String;
cell.CellValue = new CellValue(dr[column].ToString());
cell.StyleIndex = 1;
row.AppendChild(cell);
}
sheetData.AppendChild(row);
}
sheetId++;
wSheetPart.Worksheet.AppendChild(sheetData);
}
}
}
}
}
return FilePath;
}