c# The process cannot access the file because it is being used by another process. Even after closing the connection on sqlite 3

Try this In my opinion It will be better if you use using

 using (SqlConnection conn = new SqlConnection(cmn.connString))
        {
            conn.Open();
            string query = "select networkid, network from custom_networkList";
            using (SqlCommand cmd = new SqlCommand(query, conn))
            using (SqlDataReader reader = cmd.ExecuteReader())
            {
                while (reader.Read())
                {
                    int networkid = Convert.ToInt32(reader["networkid"]);
                    string network = reader["network"].ToString();

                    File.Copy(Templatefile, newfile + network + ".sqlite", true);
                    using (SQLiteConnection m_dbConnection = new SQLiteConnection(@"Data Source=" + newfile + network + ".sqlite;Version=3;"))
                    {
                        m_dbConnection.Open();
                        using (SQLiteCommand command = new SQLiteCommand("begin", m_dbConnection))
                        {
                            command.ExecuteNonQuery();

                            insertZone(m_dbConnection);
                            InsertJunctions(m_dbConnection, networkid);
                            InsertHydrant(m_dbConnection, networkid);
                            insertWaterTank(m_dbConnection, networkid);
                            insertPump(m_dbConnection, networkid);
                            InsertReservoir(m_dbConnection, networkid);
                            insertValve(m_dbConnection, networkid);
                            insertPipe(m_dbConnection, networkid);

                            using (command = new SQLiteCommand("end", m_dbConnection))
                            {
                                command.ExecuteNonQuery();
                            }
                            // m_dbConnection.Close();
                            // command.Dispose();
                        }

                    }
                }

            }
        }

        GC.WaitForPendingFinalizers();
        GC.Collect();

        if (!Directory.Exists(newfilename))
        {
            // Try to create the directory.
            File.Delete(newfilename);
        }
        ZipFile.CreateFromDirectory(newfile, newfilename, CompressionLevel.Fastest, true);
        Directory.Delete(newfile, true);

        return newfilename2;

for handle any file you have to do something like this

using (FileStream fs = File.Open(filePath, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
        {

            using (StreamReader sr = new StreamReader(fs, Encoding.Default))
            {




            }

            // or 
            using (StreamWriter sw = new StreamWriter(fs, Encoding.Default))
            {




            }


//  you can zip file or do what you want  here
        }

hope you can solve this problem

On more recent SQLite client versions, the error "The process cannot access the file '...' because it is being used by another process" can happen due to a change of behaviour: the introduction of connection pool. I have used effectively the following workaround to disable pooling by adding Pooling=false to the connection string.

From: https://github.com/dotnet/efcore/issues/27139#issuecomment-1007588298

The SQLite provider now pools connections, improving connection speed significantly but keeping connections open. You can disable pooling by adding Pooling=false to the connection string or calling SqliteConnection.ClearAllPools() at the point where you want them to be closed.

Also documented in https://docs.microsoft.com/en-us/ef/core/what-is-new/ef-core-6.0/breaking-changes#sqlite-connections-are-pooled