how to validate duplicate name file upload

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ASP.NET

Hello Friends
I want to upload a file into my projects Folder(..\TextFiles\Blogs).
But I want to upload files by unique name so that niether two files with same name
can be uploaded nor override the existing file.
My Code is as below:

protected void blgBtn_Click(object sender, EventArgs e)
       {

           string fileName = blgFile.FileName;
           string filePath = blgFile.PostedFile.FileName;
           int fileLength = blgFile.PostedFile.ContentLength;
           blgFile.SaveAs(Server.MapPath("~/TextFiles/Blogs") + fileName);
           byte[] imageBytes = new byte[fileLength];
           blgFile.PostedFile.InputStream.Read(imageBytes, 0, fileLength);

           if (System.IO.File.Exists(filePath))
           {
               int counter = 2;
               while (System.IO.File.Exists(filePath))
               {
                   // if a file with this name already exists,
                   // prefix the filename with a number.
                   string tempfileName = counter.ToString() + fileName;
                   filePath = filePath + tempfileName;
                   counter++;
               }


               cmd = new SqlCommand("AddImg", con);
               cmd.CommandType = CommandType.StoredProcedure;
               SqlParameter[] prms = new SqlParameter[5];
               //cmd.Parameters.AddWithValue("BlogName",blgTb.Text);
               cmd.Parameters.AddWithValue("BlogPath", blgFile.ToString());
               //cmd.Parameters.AddWithValue("BlogFile",imageBytes);
               cmd.Parameters.AddWithValue("Sequence", int.Parse(Seq.Text));
               cmd.Parameters.AddWithValue("Page", int.Parse(blgPage.Text));
               cmd.Parameters.AddWithValue("Date", DateTime.Parse(dtpCalendar.Text));
               cmd.Parameters.AddWithValue("Comment", blgComment.Text);
               con.Open();
               cmd.ExecuteNonQuery();
               con.Close();

If it not fine then suggest me write code.

Thanks in Advance

With Best Regards
Akhilesh Pathak