C#的資料型態對應到.NET結構，原因是為了讓C#能夠跟.net語言相容。

This design is a part of what makes your C# code portable to other .NET
languages. The C#
values map to .NET structures that can be used by any .NET language, because
any .NET
structure can be used by the CLR. Mapping C# keywords to .NET structures
also enables the
structures to use techniques such as operator overloading to define the
value's behavior when
the type is used in an expression with an operator. You'll examine operator
overloading when
you learn about C# classes.

原來C#的資料型態對應到.NET結構，原因是為了讓C#能夠跟.net語言相容。
因為.NET結構可以對應到CLR。