How to prevent duplicate upload in excel to SQL

See more:

C#

ASP.NET

WebForms

I'm trying to work with uploading excel in asp.net c# web form and save in sql however it also upload duplicate data in row.

private bool uploadfile1()
{
	try
	{
		if (FileUpload1.PostedFile.FileName != "" || FileUpload1.PostedFile.FileName != "File Template")
		{
			this.checkDirectory();
			FileUpload1.PostedFile.SaveAs(Server.MapPath("") + "\\Uploads\\" + FileUpload1.FileName);
			filename = FileUpload1.FileName;
			path = Server.MapPath("") + "\\Uploads\\";
			ExcelCS xl = new ExcelCS();
			xl.UserId = (Session["userid"] != null) ? Session["userid"].ToString() : String.Empty;
			xl.Session = (Session["sessionID"] != null) ? Session["sessionID"].ToString() : String.Empty;
			if (xl.ParseExcelFile(path + filename, true, 1))
			{
				listdata save = new listdata();
				if (save.save())
				{
					Class.JSclass.ShowAlert(save.RecordsUploaded.ToString() + " item(s) uploaded and " + save.TotalUpdated.ToString() + " item(s) updated out of " + save.TotalRecords.ToString() + " Record(s).");
					listweb.Class.Logger.writeLog(Session["userid"].ToString(), Session["sessionID"].ToString(), "frmUploadFile.uploadfile1", "File uploaded successfully!", "", "", Class.LogCategories.SELECT);
					Class.JSclass.refreshMainPage();
					return true;
				}
			}
			else
			{
				Class.JSclass.ShowAlert("Invalid file format please use specified template.");
				listweb.Class.Logger.writeLog(Session["userid"].ToString(), Session["sessionID"].ToString(), "frmUploadFile.uploadfile1.ParseExcelFile", "Error: " + xl.Message, "", "", Class.LogCategories.SELECT);
				return false;
			}
		}
	}
	catch (Exception e)
	{
		Class.JSclass.ShowAlert("Error: " + e.Message);
		listweb.Class.Logger.writeLog(Session["userid"].ToString(), Session["sessionID"].ToString(), "frmUploadFile.uploadfile1", "Error: " + e.Message, "", "", Class.LogCategories.SELECT);
	}

	Class.JSclass.ShowAlert("File upload failed!");
	return false;
}

What I have tried:

I tried only tried to save the upload in sql however with duplicate/ same data in upload/save in sql. I wanted to void the duplication of the data