Извлечение pdf файла из SQL C#

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Some help please
 
Insert into sql

yte[] filedata = null;  
           MemoryStream ms = new MemoryStream();  
           filedata = ms.GetBuffer();  
           axAcroPDF1.src = LocalEncoding.GetString(ms.ToArray());  
  
  
                   using (SqlConnection openCon = new SqlConnection(cs))  
                   {  
  
                       string saveStaff = "declare @maxNo integer = 0 select @maxNo = isnull(max(number), 0) from [dbo].[documents]; Set @maxNo=@maxNo+1; INSERT into dbo.documents (number, file_location, pdf_file) VALUES (@maxNo,@file_location,@pdf_file)";  
  
                       using (SqlCommand querySaveStaff = new SqlCommand(saveStaff))  
                       {  
                           querySaveStaff.Connection = openCon;                            
                           querySaveStaff.Parameters.Add("@file_location", SqlDbType.VarChar, 255).Value = file_locationTextBox.Text;  
                           querySaveStaff.Parameters.AddWithValue("@pdf_file",SqlDbType.VarBinary).Value=filedata;  
  
                           openCon.Open();  
                           querySaveStaff.ExecuteNonQuery();  
                           openCon.Close();  
  
                             
  
                       }  
  
                   }  
               }  

Что я уже пробовал:

Выбор изменил datagrid поставьте этот код

Error is when retrieve file...(no have error) noting hapend....what I wrong?
 
I think at line 3 to line 9

try  
                {  
                     if (documentsDataGridView.SelectedRows[0].Cells["pdf_file"].Value != null)  
                     {  
                        byte[] ap = (byte[])documentsDataGridView.SelectedRows[0].Cells["pdf_file"].Value;  
                        MemoryStream ms = new MemoryStream(ap);  
                        axAcroPDF1.src = LocalEncoding.GetString(ms.ToArray());  
                          
                    }  
                    else {  
                         axAcroPDF1.src = null;  
                     }  
                }  
                catch  
                {  
                    axAcroPDF1.src = null;  
                }  

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