C#

//both these classes implement the ISaveAsWordDocument interface, but they are 
//totally diferent under the hood. the ISaveAsWordDocument interface defines a 
//method called Save(), all classes using this interface must implimemt that
//method and it is expected to save its contents to a word document.

ISaveAsWordDocument[] docs = new ISaveAsWordDocument[3];

//LotsOfText, GraphsAndStuff, and Book implement("inherit") the
//ISaveAsWordDocumnet interface
docs[0] = new LotsOfText();
docs[1] = new GraphsAndStuff();
docs[2] = new Book();

//as you can see interfaces allow you to do operations an ANY type that
//implements that interface, no casting or anything like that is needed.
foreach(ISaveAsWordDocument doc in docs)
 doc.Save("document ... .doc");

static int Sqrt(int x) { if (x<0) throw new ArgumentOutOfRangeException(); int temp, y=0, b=0x8000, bshft=15, v=x; do { if (v>=(temp=(y<<1)+b<<bshft--)) {="" y+="b;" v-="temp;" }="" while="" ((b="">>=1)>0); return y;

<br />
doc.Load("123.xml");<br />

XmlNode node = doc.SelectSingleNode("/app-settings/monitors/file");

Stefan Troschütz wrote:

First of all "it doesn't work." isn't very descriptive. So the next time explain in more detail what's wrong.