Download / Upload any file and Display Message using C# in ASP.NET

* To display information using message box in ASP.NET page from server side code.

static public void DisplayAJAXMessage(Control page, string msg)
    {
            string myScript = String.Format("alert('{0}');", msg);
            ScriptManager.RegisterStartupScript(page, page.GetType(), "MyScript", myScript, true);      
    }

e.g. : DisplayAJAXMessage(this, "Hello World");
OUTPUT: 

Fig 1: Output of DisplayAjaxMessage

* Download a file from server using link button:

protected void lnkDownloadFile_Click(object sender, EventArgs e)
    {
        try
        {
            string FileName = string.Empty;
            FileName = "demo.xls"; // Any File Name with extension
            string link = Server.MapPath("<~/Folder Name/>" + FileName); //Optional Folder Name
            FileInfo myfile = new FileInfo(link);
            Response.AddHeader("Content-Disposition", "attachment; filename=" + myfile.Name);
            Response.AddHeader("Content-Length", myfile.Length.ToString());
            Response.ContentType = ReturnExtension(myfile.Extension.ToLower());
            Response.TransmitFile(myfile.FullName);
            Response.Flush();
            Response.End();
        }
        catch (Exception ex)
        {
            DisplayAJAXMessage(this, "File Not Found");
        }
    }

private string ReturnExtension(string fileExtension)
    {
        switch (fileExtension)
        {
            case ".xls":
                // case ".csv":
                return "application/vnd.ms-excel";
            default:
                return "application/octet-stream";
        }
    }

* Upload any file to server using C# in ASP.NET 
(Note: This example shows to upload excel file (.xls) , Just change the extension of file as per requirement to upload any type file.)

  protected void btnSave_Click(object sender, EventArgs e)
    {
        try
        {
            if (UploadFile.HasFile) //FileUpload tool from ToolBox
            {
                string Extension = Path.GetExtension(UploadFile.PostedFile.FileName);
                if (Convert.ToString(Extension).ToLower() != ".xls")
                {
                    lblError.Text = "Please select a file with extension .xls before validation";
                    return;
                }
            }
            else
            {
                lblError.Text = "Please select a file with extension .xls before validation";
                return;
            }
            string uploadFileName = Path.GetFileName(UploadFile.PostedFile.FileName);
            int index = uploadFileName.LastIndexOf('.');
            string SheetName = uploadFileName.Substring(0, index);
            string FileName = Path.GetFileName(UploadFile.PostedFile.FileName);
            string FilePath = Server.MapPath("~//" + FileName); //Optional FolderName
            UploadFile.SaveAs(FilePath);
         }
        catch (Exception ex)
        {
           DisplayAJAXMessage(this,"Error::"+ex);
        }
    }

Happy Coding 

Software Developer, Academic Writing Writer

Display a file in NewPage and export a file to Excel.

Display a file on Link Button Click.

protected void linkbtnFile_Click(object sender, EventArgs e)
    {
        string link =  Server.MapPath(".") + "\\\\" +;
        Response.ContentType = "application/"+linkbtnFile.Text.Substring(linkbtnFile.Text.IndexOf('.')+1);
        Response.AppendHeader("Content-Disposition", "attachment; filename=" + link);
        Response.TransmitFile(link);
        Response.End();
    }

Export a File from Radgrid to Excel file.

protected void btnExport_Click(object sender, EventArgs e)
    {
        RadGrid1.MasterTableView.ExportToExcel();
        RadGrid1.ExportSettings.ExportOnlyData = true;
        RadGrid1.ExportSettings.IgnorePaging = true;
        RadGrid1.ExportSettings.OpenInNewWindow = true;
    }

Export data from GridView/DataTable to Excel File using C#.NET for webpage and VB.NET window based application

How to Export GridViewData to Excel File using C#.NET ?

Step 1 : Create a function for Change Controls To Value :

private void ChangeControlsToValue(Control gridView)
    {
        Literal literal = new Literal();
       
        for (int i = 0; i < gridView.Controls.Count; i++)
        {
            if (gridView.Controls[i].GetType() == typeof(LinkButton))
            {

                literal.Text = (gridView.Controls[i] as LinkButton).Text;
                gridView.Controls.Remove(gridView.Controls[i]);
                gridView.Controls.AddAt(i,literal);
            }
            else if (gridView.Controls[i].GetType() == typeof(DropDownList))
            {
                literal.Text = (gridView.Controls[i] as DropDownList).SelectedItem.Text;

                gridView.Controls.Remove(gridView.Controls[i]);

                gridView.Controls.AddAt(i,literal);

            }
            else if (gridView.Controls[i].GetType() == typeof(CheckBox))
            {
                literal.Text = (gridView.Controls[i] as CheckBox).Checked ? "True" : "False";
                gridView.Controls.Remove(gridView.Controls[i]);
                gridView.Controls.AddAt(i,literal);
            }
            if (gridView.Controls[i].HasControls())
            {

                ChangeControlsToValue(gridView.Controls[i]);

            }

        }

    }

Step 2 : On Button Click to export data, Add the following Code :

protected void btnExportToExcel_Click(object sender, EventArgs e)
    {
        if (RadioButtonList1.SelectedIndex == 0)
        {
            GridView1.AllowPaging = false;
            GridView1.GridLines = GridLines.None;
            GridView1.DataBind();
        }
        else
        {
            GridView1.PagerSettings.Visible = false;
            GridView1.GridLines = GridLines.None;
            GridView1.DataBind();
        }

        ChangeControlsToValue(GridView1);
        Response.ClearContent();

        Response.AddHeader("content-disposition", "attachment; filename=GridViewToExcel.xls");

        Response.ContentType = "application/excel";

        StringWriter sWriter = new StringWriter();

        HtmlTextWriter hTextWriter = new HtmlTextWriter(sWriter);

        HtmlForm hForm = new HtmlForm();

        GridView1.Parent.Controls.Add(hForm);

        hForm.Attributes["runat"] = "server";

        hForm.Controls.Add(GridView1);

        hForm.RenderControl(hTextWriter);
       
        // Write below code to add cell border to empty cells in Excel file
        // If we don't add this line then empty cells will be shown as blank white space

        StringBuilder sBuilder = new StringBuilder();
        sBuilder.Append(" <!--[if gte mso 9]>ExportToExcel<![endif]");
        sBuilder.Append(sWriter + "-->");

        Response.Write(sBuilder.ToString());

        Response.End();
    }

 Export data from data table to excel file in window based application using VB.NET

Private Sub exporttoexcel(ByVal dtable As DataTable)

        Dim strTempFile As String = My.Computer.FileSystem.GetTempFileName()

        Dim strLine As New Text.StringBuilder("")

        For c As Integer = 0 To dtable.Columns.Count - 1
            strLine.Append(dtable.Columns(c).ColumnName.ToString & ",")
        Next

        My.Computer.FileSystem.WriteAllText(strTempFile, strLine.ToString.TrimEnd(",") & vbCrLf, True)

        For r As Integer = 0 To dtable.Rows.Count - 1
            strLine = New Text.StringBuilder("")
            For c As Integer = 0 To dtable.Columns.Count - 1
                strLine.Append(dtable.Rows(r).Item(c).ToString & ",")
            Next

            My.Computer.FileSystem.WriteAllText(strTempFile, strLine.ToString.TrimEnd(",") & vbCrLf, True)
        Next

        Process.Start("excel", strTempFile)
    End Sub
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Call this function on button click event to export the rows of the data table to excel file