Create Thumbnail in asp.net

System.Drawing.Image img = System.Drawing.Image.FromStream(FileUpload.InputStream);
 System.Drawing.Image thumbnailImage = img.GetThumbnailImage(25, 30, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);
   img.save(stringPath);

select all checkbox in asp.net

 function SelectAll(id)
{
        var frm = document.forms[0];
        for (i=0;i
    {
            if (frm.elements[i].type == "checkbox")
        {
                frm.elements[i].checked = document.getElementById(id).checked;
                }
        }
}  

Place this text in your source File :

{         
          //  HeaderTemplate in tag <>  //

 // asp:CheckBox ID="chkAll" runat="server"  in tag <>//

 //  HeaderTemplate in tag <>//

      

}   
In Code File

  protected void grdmember_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.Header)
        {
            //adding an attribute for onclick event on the check box in the header
            //and passing the ClientID of the Select All checkbox
            ((CheckBox)e.Row.FindControl("chkAll")).Attributes.Add("onclick", "javascript:SelectAll('" + ((CheckBox)e.Row.FindControl("chkAll")).ClientID + "')");
        }
    }

How to Download File from asp.net

string st, doctitle;
doctitle = e.CommandArgument.ToString();
st = Server.MapPath("../documents") + "//" + doctitle;
FileInfo f = new FileInfo(st);
if (f.Exists == true)
{
Response.Clear();
Response.AddHeader("content-disposition", "attachment;filename=" + f.Name);
Response.AddHeader("content.length", f.Length.ToString());
Response.ContentType = "application/octet-stream";
Response.WriteFile(f.FullName);
Response.End();
}