filtering specific lines in C#

I have searched but did not find a solid solution for my project that works. What I want to do is open up a text file and filter it for only lines that start with "description".

This is only a small sample of whats in my text file:

interface Ethernet1/5
  description INFRA:TRUNK:myserver4
  switchport mode trunk
  switchport trunk native vlan 64
  spanning-tree mst pre-standard
  spanning-tree guard root
  udld aggressive
  no shutdown

 interface Ethernet1/6
  description INFRA:TRUNK:easyserver99
  switchport mode trunk
  switchport trunk native vlan 99
  spanning-tree mst pre-standard
  spanning-tree guard root
  udld aggressive
  no shutdown

This is my code th开发者_如何学运维at I am using right now but it is not getting the job done.

private void scrapeConfig_Click(object sender, EventArgs e)

    {
    string textline;
    string description;

    //Open and read file
    System.IO.StreamReader objReader;
    objReader = new System.IO.StreamReader(Chosen_File);
    textBox1.Text = objReader.ReadToEnd();

    //Scrape for certain lines
    do
    {
    textline = objReader.ReadLine() + "\r\n";
    textBox1.Text = textline;
    } while (objReader.Peek() != -1);

    //Close
    objReader.Close();
}

Thank you for your help in advance!

var lines = File.ReadAllLines(filepath)
                .Select(l=>l.Trim())
                .Where(l=>l.StartsWith("description"));
textBox1.Text = String.Join(Environment.NewLine, lines);