How to programmatically attach a document or file in a SPListItem

How to programmatically attach a document or file in a SPListItem

In this post I discussed, how we can programmatically attach a document or file in a SPListItem of SPList (SharePoint's List).

Following method contains the logic to attach the document / file (codes with comments are self-explainatory).

    /// <summary>
    /// Programmatically Attach document in SPDocument Library 
    /// </summary>
    void documentAttachmentInSPList()
    {
        //SPListItem spListItem = null; //write code to get the SPListItem.
        //fileUpload is control ID of ASP.Net FileUpload control        
        if (!string.IsNullOrEmpty(fileUpload.FileName))
        {
            //Get file extension ( *.doc OR *.docx )
            string fileExtension 
             = fileUpload.FileName.Substring(fileUpload.FileName.IndexOf("."));

            //FILENAME is file name visible in SPListItem
            //Check file is already added or not. If added then delete it.
            for (int i = 0; i < spListItem.Attachments.Count; i++)
            {
                if ((spListItem.Attachments[i] != null) 
                    && (spListItem.Attachments[i].Equals("FILENAME" + fileExtension)))
                {
                    spListItem.Attachments.Delete("FILENAME" + fileExtension);
                    break;
                }
            }

            //Attach the file.
            spListItem.Attachments.Add("FILENAME" + fileExtension, fileUpload.FileBytes);
            
            //LISTNAME is SPList's name
            //See the attached file as link in user-created custom column.
            string attachmentURL = Request.Url.Scheme + "://" + Request.Url.Authority
                   + "/Lists/" + "LISTNAME" + "/Attachments/" + spListItem.ID + "/";

            spListItem["Attached File"] 
              = attachmentURL + "FILENAME" + fileExtension + ", View FILE";
        }
    }