C#

RichTextBox rtb = new RichTextBox(); rtb.Text = richTextBox1.Text;

RichTextBox rtb = new RichTextBox(); rtb = richTextBox1;

richTextBox1.Text = alltxt;

int posTxt = 0; string tempText = "";
        private void button2_Click(object sender, EventArgs e)
        {
            richTextBox1.Text = tempText;//somewhere in the page load : tempText = richTextBox1.Text;

            string searchText = textBox2.Text.ToLower();
            string alltxt = richTextBox1.Text.ToLower();

            if (alltxt.Contains(searchText))
            {
                //problems at start
                if (posTxt <= 0)
                {
                    richTextBox1.Text = richTextBox1.Text.Insert(0, " "); 
                    posTxt = 1;
                }
                //colorization at found text 
                while (posTxt > 0)
                {
                    posTxt = richTextBox1.Find(searchText, posTxt, RichTextBoxFinds.None);
                    if (richTextBox1.SelectedText.ToLower() == searchText)
                    {
                        richTextBox1.SelectionLength = searchText.Length;
                        richTextBox1.SelectionColor = Color.Red;
                    }
                    posTxt = richTextBox1.Find(searchText, posTxt + 1, RichTextBoxFinds.None);
                }
            }
            posTxt = 0;
        }

^\d+$

^[0-9]

if(s.Length == 0) return neither;
else if(s[0] == '-') return negative;
else if(s[0] >= '0' && s[0] <= '9') return positive;
else return non-numeric;

List<SalesTeam> teamNorth;
List<SalesTeam> teamSouth;
List<SalesTeam> teamEast;

class SalesTeam {
	public string name;
}
class SalesTeamNorth : SalesTeam {
	public SalesTeamNorth(int v) { name="N"+v; }
}
class SalesTeamSouth : SalesTeam {
	public SalesTeamSouth(int v) { name="S"+v; }
}
public override void Test(int arg) {
	List<SalesTeam> teamsNorth=new List<SalesTeam>();
	for(int i=0; i<3; i++) teamsNorth.Add(new SalesTeamNorth(i));
	List<SalesTeam> teamsSouth=new List<SalesTeam>();
	for (int i=0; i<3; i++) teamsSouth.Add(new SalesTeamSouth(i));
	
	// now iterate all teams
	foreach (List<SalesTeam> teams in new List<List<SalesTeam>>(){ teamsNorth, teamsSouth }) {
		foreach (SalesTeam team in teams) {
			log(team.name);
		}
	}
}