C# DataGirdview手动添加数据，导出txt文件并自动对齐

//DataGirdview手动添加数据

 private void btnDataGirdView_Click(object sender,EventArgs e)

    {
      dataGridView1.Columns.Add("a","标题1");
      dataGridView1.Columns.Add("b","标题2");
      dataGridView1.Columns.Add("c","标题3");

      string[] dr1= { "1","22","3333" };
      string[] dr2= { "4444","55","6" };


      DataGridViewRow Row=new DataGridViewRow();
      int index=dataGridView1.Rows.Add(Row);
      dataGridView1.Rows[index].Cells[0].Value=dr1[0].ToString();
      dataGridView1.Rows[index].Cells[1].Value=dr1[1].ToString();
      dataGridView1.Rows[index].Cells[2].Value=dr1[2].ToString();


      DataGridViewRow Row2=new DataGridViewRow();
      int index2=dataGridView1.Rows.Add(Row2);
      dataGridView1.Rows[index2].Cells[0].Value=dr2[0];
      dataGridView1.Rows[index2].Cells[1].Value=dr2[1];
      dataGridView1.Rows[index2].Cells[2].Value=dr2[2];  
    }

//DataGirdview导出txt文件，并自动对齐
    private void btnOutPutText_Click(object sender,EventArgs e)
    {
      string FullFileName=@"D:aaa.txt";
     // FileStream fs=new FileStream(FullFileName,FileMode.CreateNew);
      StreamWriter sw=new StreamWriter(FullFileName,true,Encoding.Default);
      string str="";
      for(int i=0;i<dataGridView1.Rows.Count-1;i++)
      {
        for(int j=0;j<dataGridView1.Columns.Count;j++)
        {
         str=dataGridView1.Rows[i].Cells[j].Value.ToString().Trim();
         if(str.Length<10)
           str=str.PadRight(10,' ');
         str=str+"|";
          sw.Write(str);
        }
        sw.WriteLine("");
      }
      sw.Close();
    }