I think maybe you don't understand how interfaces work. An interface basically tells you that a type implementing it is guaranteed to have a specific set of members. The interface guarantees that those members will exist but it doesn't provide any implementation or place any restrictions on what implementations can be used. In order for your code to work, you must first define a class that implements the IExample interface and then you must create an instance of that class and assign it to your variable.
With just that information, many wonder what use interfaces are when they start out. One of the most obvious examples that I can think of is when using data-binding in Windows Forms. The DataSource property of controls like ComboBox, ListBox and DataGridView is type Object. That means that you can theoretically assign any object to that property. If the object you assign does not implement either the IList or IListSource interface though, an exception will be thrown. That's because, internally, those controls assume that the set of members defined by the IList interface will be accessible. It doesn't care how they're implemented; only that they're there.
