.NET Base Class Library, C#, and CIL Data Type Mappings

Table 17-4 illustrates how a .NET base class type maps to the corresponding C# keyword, and how each C# keyword maps into raw CIL. As well, Table 17-4 documents the shorthand constant notations used for each CIL type. As you will see in just a moment, these constants are often referenced by numerous CIL opcodes.

Table 17-4. Mapping .NET Base Class Types to C# Keywords, and C# Keywords to CIL

.NET Base Class Type	C# Keyword	CIL Representation	CIL Constant Notation
System.SByte	sbyte	int8	I1
System.Byte	byte	unsigned int8	U1
System.Int16	short	int16	I2
System.UInt16	ushort	unsigned int16	U2
System.Int32	int	int32	I4
System.UInt32	uint	unsigned int32	U4
System.Int64	long	int64	I8
System.UInt64	ulong	unsigned int64	U8
System.Char	char	char	CHAR
System.Single	float	float32	R4
System.Double	double	float64	R8
System.Boolean	bool	bool	BOOLEAN
System.String	string	string	N/A
System.Object	object	object	N/A
System.Void	void	void	VOID

Note The System.IntPtr and System.UIntPtr types map to native int and native unsigned int (this is good to know, as many of COM interoperability and P/Invoke scenarios use these extensively).