Foreach преобразование типа char к string невозможно - C#

private void button3_Click(object sender, EventArgs e)
        {
            saveFileDialog1.DefaultExt = "txt";
            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                string filename = saveFileDialog1.FileName;
                StreamWriter sw = new StreamWriter(filename);
                string start_time = "Нет доступа к информации о процессе";
                foreach (var winProc in Process.GetProcesses())
                {
 
                    try
                    {
 
                        start_time = winProc.StartTime.ToString();
 
                    }
                    catch (Exception er)
                    {
 
                    }
 
                    sw.WriteLine(winProc.Id.ToString() + "Имя: " + winProc.ProcessName + ", Время старта: " + start_time);
                    using (System.IO.StreamWriter file =
           new System.IO.StreamWriter(@"C:\Users\Мрр\Documents\WriteLines2.txt"))
                    {
                        foreach (string line in filename)
                        {
                            // If the line doesn't contain the word 'Second', write the line to the file.
                            if (!line.Contains(winProc.Id.ToString()))
                            {
                                file.WriteLine(line);
                            }
                        }
                    }
                }
 
                sw.Close();
               
            }