Methods

StringBuilder.Append :

Append information to the end of the current StringBuilder.

StringBuilder.AppendFormat :

Replace a formate specifier passed in a string with formatted text.

StringBuilder.Insert :

Inserts a string or object into the specified index of the current.

StringBuilder.Remove :

Remove a specified number of a characters from the current StringBuilder.

StringBuilder.Replace :

Replace a specified character at a specified index.

A simple program using String Builder class :

using System;
using System.Text;

class StringDemo {
	public static void Main () {
		string str ="www.Scanftree.com";
		StringBuilder revStr=new StringBuilder();
		for (int count=str.Length-1;count>-1 count--) {
			revStr.Append(str[count]);
		}
		Console.WriteLine(revStr.ToString());
		Console.ReadLine();
	}
}

using System;
using System.Text;

class StringBuilderDemo1 {
	public static void Main() {
		StringBuilder myStringBuilder=new StringBuilder();
		myStringBuilder.Append("myString");
		myStringBuilder.Append("here is another String ", 0,4);
		Console.WriteLine(myStringBuilder);
		Console.ReadLine();
	}
}