Answer 1)
The CLS (Common Language Specification) lays the groundwork for a common set of rules for compliance that guarantees that other languages (VB.NET, F#, etc.) can use assemblies that you have built with C#.
Here is an example that is easier to understand:
class Foo
{
public void Bar() { }
public void bar() { }
}
This type would not be CLS compliant since it contains two members that differ in name only by type. How would someone using VB.NET disambiguate between Bar and bar since the VB.NET compiler is not case-sensitive?
So basically the CLS is a bunch of rules like this to guarantee interoperability between languages.
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