C# - import file .txt into DataGridView รบกวนช่วยหน่อยนะครับ

private void button1_Click(object sender, EventArgs e)
        {
            string strValue = "";
            List<int> rowsToDelete = new List<int>();
            {
                foreach (DataGridViewRow row in dataGridView1.Rows)
                {
                    DataGridViewCheckBoxCell checkBox = dataGridView1[0, row.Index] as DataGridViewCheckBoxCell;
                    if (checkBox != null) 
                    {
                        if (Convert.ToBoolean(checkBox.Value) == true)
                        {
                            strValue += ";" + row.Cells[1].Value.ToString();
                            
                            StreamWriter File = new StreamWriter("Test_File1.txt");
                            File.Write(strValue);
                            File.Close();
                        }
                    }
                }
            }
        }