搜索已创建的文件

当我创建文件并将其余信息附加到文件中时,我现在希望能够读取文本文件,然后显示文件中列出的生日月份。 我想在生日前把信息输入。所以如果我选择第11个月,我想通过按按钮4来输入出生月份为11的所有数据条目。

这就是我目前为止所拥有的;

 private void close_Click(object sender, EventArgs e)
    {
        Close();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        writetext();
        reset();

    }
    public void writetext()
    {

        using (TextWriter writer = File.AppendText("filename.txt"))

        {
         writer.WriteLine("First name, {0} Lastname, {1} Phone,{2} Day of birth,{3} Month of Birth{4}", textBox1.Text, textBox2.Text, maskedTextBox1.Text, textBox4.Text, textBox3.Text);
         MessageBox.Show(String.Format("First Name,{0} Lastname, {1} Phone,{2} Day of birth,{3} Month of Birth{4}", textBox1.Text, textBox2.Text, maskedTextBox1.Text, textBox4.Text, textBox3.Text)); 
        }
        }
    public void reset()
    {
        textBox1.Text = "";
        textBox2.Text = "";
        textBox3.Text = "";
        textBox4.Text = "";
        maskedTextBox1.Text = "";
    }

    private void button3_Click(object sender, EventArgs e)
    {
        Close(); 
     }

    private void button2_Click(object sender, EventArgs e)


    {
        readfile(); 


    }

    private void label7_Click(object sender, EventArgs e)
    {

    }

    private void button4_Click(object sender, EventArgs e)
    {

    }
    public void readfile()
    {
        string[] lines = File.ReadAllLines("filename.txt");
        label6.Text = String.Join(Environment.NewLine, lines);
    }
}






 }