Share your code.

Or try with below article.

Export DataTable to Excel in ASP.Net using C# and VB.Net

Hi Dharmendr

Please find the code below 

For both RDLC Report Export To Excel and Below Button Click the downloaded file has same issue. 

Is there something else I can try 

Thanks for your help  

Dim connection As String = ConfigurationManager.ConnectionStrings("ConnectionStringDirect").ConnectionString
        Using con As New SqlConnection(connection)
            Using cmd As New SqlCommand("Select Statement")
                con.Open()
                cmd.Connection = con
                Dim sda As New SqlDataAdapter
                sda.SelectCommand = cmd
 
                Using dt As New DataTable()
                    dt.Columns.AddRange(New DataColumn() {New DataColumn("COL0", GetType(String)), New DataColumn("COL1", GetType(String)), New DataColumn("COL2", GetType(String)), New DataColumn("COL3", GetType(String)), New DataColumn("COL4", GetType(String)), New DataColumn("COL5", GetType(String)), New DataColumn("COL6", GetType(String))})
                    sda.Fill(dt)
                    Using wb As New XLWorkbook()
                        Dim ws = wb.Worksheets.Add(dt, "EMS")
 
                        If dt.Rows.Count > 0 Then
                            ws.Cell("A1").Value = dt.Columns(0).ColumnName
                            ws.Cell("B1").Value = dt.Columns(1).ColumnName
                            ws.Cell("C1").Value = dt.Columns(2).ColumnName
                            ws.Cell("D1").Value = dt.Columns(3).ColumnName
                            ws.Cell("E1").Value = dt.Columns(4).ColumnName
                            ws.Cell("F1").Value = dt.Columns(5).ColumnName
                            ws.Cell("G1").Value = dt.Columns(6).ColumnName
 
                            For i As Integer = 0 To dt.Rows.Count - 1
                                ws.Cell("A" & (i + 2)).Value = dt.Rows(i)(0)
                                ws.Cell("B" & (i + 2)).Value = dt.Rows(i)(1)
                                ws.Cell("b" & (i + 2)).Style.DateFormat.Format = "dd/MM/yyyy"
                                ws.Cell("C" & (i + 2)).Value = dt.Rows(i)(2)
                                ws.Cell("E" & (i + 2)).Value = dt.Rows(i)(4)
                                ws.Cell("e" & (i + 2)).Style.DateFormat.Format = "dd/MM/yyyy"
                                ws.Cell("F" & (i + 2)).Value = dt.Rows(i)(5)
                                ws.Cell("f" & (i + 2)).Style.DateFormat.Format = "dd/MM/yyyy"
                            Next
                        End If
 
 
                        ws.Table(0).ShowAutoFilter = False ' Disable AutoFilter.
                        ws.Table(0).Theme = XLTableTheme.None ' Remove Theme.
                        ws.Columns().AdjustToContents() ' Resize all columns.
 
                        Response.Clear()
                        Response.ClearContent()
                        Response.Buffer = True
                        Response.Charset = ""
                        Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                        Response.AddHeader("content-disposition", "attachment;filename=SqlExport.xlsx")
                        Using MyMemoryStream As New MemoryStream()
                            wb.SaveAs(MyMemoryStream)
                            MyMemoryStream.WriteTo(Response.OutputStream)
                            Response.Flush()
                            Response.End()
                        End Using
                    End Using
                End Using
            End Using
        End Using
    End Sub

Refer:

1. Set Date Format while exporting DataTable to Excel using ClosedXML in ASP.Net

2. Remove all style and Table format when exporting to Excel using ClosedXML in ASP.Net

If this will not resolve your issue share the upload code.

Hi Dharmendr

Once again thanks for your prompt reply.  I have tired both the styles before and now again as well but still not luck. The files do get downloaded with correct data but issue when i upload the file it does not read until I click and save it again. 

IN the link below is the file I want to upload and in this state it will not upload correctly unless I save it (after double clicking on any cell) 

Link To File

Please share the code you are using to read the excel.