By using interfaces, you can, for example, include behavior from multiple sources in a class. That capability is important in C# because the language doesn’t support multiple inheritance of classes.

A controversial new proposal for .NET suggests the introduction of a limited form of multiple inheritance via abstract interfaces. This feature was inspired by Java’s default methods.

Part 6: Use interfaces for safe multiple inheritance and a great deal more; Part 7: Learn about Java’s many shapes and find out how to accommodate generalities in your class hierarchies; ...