substring in c# example without string functions.

txtemail.Text.Substring(0, 3);

private void button1_Click(object sender, EventArgs e)

{

  string str1 = "substring";

  char substr;

  int count = 0;

  bool flag = true;

  foreach (char c in str1)

    count++;

  for (int i=0,j=3;j<=count -1;i++, j++)

    substr=str1[j]; //Here u can get 4th character to last character

  MessageBox.Show  ("Sub String=" & substr.toString);

}