Read an Excel file uploaded using FileUpload Control without saving it on the server

Accepted answer +24 upvotes

You can use the InputStream property of the HttpPostedFile to read the file into memory.

Here’s an example which shows how to create a DataTable from the IO.Stream of a HttpPostedFile using EPPlus:

protected void UploadButton_Click(Object sender, EventArgs e)
{
    if (FileUpload1.HasFile && Path.GetExtension(FileUpload1.FileName) == ".xlsx")
    {
        using (var excel = new ExcelPackage(FileUpload1.PostedFile.InputStream))
        {
            var tbl = new DataTable();
            var ws = excel.Workbook.Worksheets.First();
            var hasHeader = true;  // adjust accordingly
            // add DataColumns to DataTable
            foreach (var firstRowCell in ws.Cells[1, 1, 1, ws.Dimension.End.Column])
                tbl.Columns.Add(hasHeader ? firstRowCell.Text
                    : String.Format("Column {0}", firstRowCell.Start.Column));

            // add DataRows to DataTable
            int startRow = hasHeader ? 2 : 1;
            for (int rowNum = startRow; rowNum <= ws.Dimension.End.Row; rowNum++)
            {
                var wsRow = ws.Cells[rowNum, 1, rowNum, ws.Dimension.End.Column];
                DataRow row = tbl.NewRow();
                foreach (var cell in wsRow)
                    row[cell.Start.Column - 1] = cell.Text;
                tbl.Rows.Add(row);
            }
            var msg = String.Format("DataTable successfully created from excel-file. Colum-count:{0} Row-count:{1}",
                                    tbl.Columns.Count, tbl.Rows.Count);
            UploadStatusLabel.Text = msg;
        }
    }
    else 
    {
        UploadStatusLabel.Text = "You did not specify a file to upload.";
    }
}

Here’s the VB.NET version:

Sub UploadButton_Click(ByVal sender As Object, ByVal e As System.EventArgs)
    If (FileUpload1.HasFile AndAlso IO.Path.GetExtension(FileUpload1.FileName) = ".xlsx") Then
        Using excel = New ExcelPackage(FileUpload1.PostedFile.InputStream)
            Dim tbl = New DataTable()
            Dim ws = excel.Workbook.Worksheets.First()
            Dim hasHeader = True ' change it if required '
            ' create DataColumns '
            For Each firstRowCell In ws.Cells(1, 1, 1, ws.Dimension.End.Column)
                tbl.Columns.Add(If(hasHeader,
                                   firstRowCell.Text,
                                   String.Format("Column {0}", firstRowCell.Start.Column)))
            Next
            ' add rows to DataTable '
            Dim startRow = If(hasHeader, 2, 1)
            For rowNum = startRow To ws.Dimension.End.Row
                Dim wsRow = ws.Cells(rowNum, 1, rowNum, ws.Dimension.End.Column)
                Dim row = tbl.NewRow()
                For Each cell In wsRow
                    row(cell.Start.Column - 1) = cell.Text
                Next
                tbl.Rows.Add(row)
            Next
            Dim msg = String.Format("DataTable successfully created from excel-file Colum-count:{0} Row-count:{1}",
                                    tbl.Columns.Count, tbl.Rows.Count)
            UploadStatusLabel.Text = msg
        End Using
    Else
        UploadStatusLabel.Text = "You did not specify an excel-file to upload."
    End If
End Sub

For the sake of completeness, here’s the aspx:

<div>
   <h4>Select a file to upload:</h4>

   <asp:FileUpload id="FileUpload1"                 
       runat="server">
   </asp:FileUpload>

   <br /><br />

   <asp:Button id="UploadButton" 
       Text="Upload file"
       OnClick="UploadButton_Click"
       runat="server">
   </asp:Button>    

   <hr />

   <asp:Label id="UploadStatusLabel"
       runat="server">
   </asp:Label>        
</div>