Exporting Datatable to Excel gives Exception from HRESULT: 0x800A03EC part way through

Question

I'm trying to export a DataTable to Excel 2007. When I get to the Excel.Range line i partially exports the Array I created but then gives me an error (System.Runtime.InteropServices.COMException (0x800A03EC): Exception from HRESULT: 0x800A03EC). I'm able to see the Data in the Excel sheet and this error happens at Row 75 of the exported data. The value that it is dying on is ===> WATCH FOR CHANGES IN SEEPAGE - SUBSTANTIAL SEEPAGE OCCURS DOWNSTREAM OF THE EMBANKMENT, EAST SIDE OF DANIELS CREEK.

The value for the ExcelRange string is A1:CL1132.

Private Sub ExportExcelFast(ByVal dt As DataTable)
  Try


        Dim Excel As New Excel.Application
        Dim Wb As Microsoft.Office.Interop.Excel.Workbook
        Dim Ws As Microsoft.Office.Interop.Excel.Worksheet

        Excel.SheetsInNewWorkbook = 1
        Excel.Workbooks.Add()
        Excel.Worksheets.Select()
        Excel.Visible = True


        Dim col, row As Integer
        ' Copy the DataTable to an object array
        Dim rawData(dt.Rows.Count, dt.Columns.Count - 1) As Object

        ' Copy the column names to the first row of the object array
        For col = 0 To dt.Columns.Count - 1
            rawData(0, col) = dt.Columns(col).ColumnName.ToUpper
        Next



        ' Copy the values to the object array
        For col = 0 To dt.Columns.Count - 1
            For row = 0 To dt.Rows.Count - 1
                rawData(row + 1, col) = dt.Rows(row).ItemArray(col)
            Next
        Next


        ' Calculate the final column letter
        Dim finalColLetter As String = String.Empty
        finalColLetter = ExcelColName(dt.Columns.Count)

        Dim excelRange As String = String.Format("A1:{0}{1}", _
                                   finalColLetter, dt.Rows.Count + 1)

        Excel.Range(excelRange, Type.Missing).Value2 = rawData
        System.Runtime.InteropServices.Marshal.ReleaseComObject(Excel)

    Catch ex As Exception

            Throw

    End Try
End Sub

Public Function ExcelColName(ByVal Col As Integer) As String
    If Col < 0 And Col > 256 Then
        MsgBox("Invalid Argument", MsgBoxStyle.Critical)
        Return Nothing
        Exit Function
    End If
    Dim i As Int16
    Dim r As Int16
    Dim S As String
    If Col <= 26 Then
        S = Chr(Col + 64)
    Else
        r = CShort(Col Mod 26)
        i = CShort(System.Math.Floor(Col / 26))
        If r = 0 Then
            r = 26
            i = CShort(i - 1)
        End If
        S = Chr(i + 64) & Chr(r + 64)
    End If
    ExcelColName = S
End Function

Answer 1

Apparently Excel does not like you entering = as the first character in a cell. Replacing the first = with '= the problem is solved.