System.Reflection.Metadata.ConstantTypeCode
Boolean = 2
Byte = 5
Char = 3
Double = 13
Int16 = 6
Int32 = 8
Int64 = 10
Invalid = 0
NullReference = 18
SByte = 4
Single = 12
String = 14
UInt16 = 7
UInt32 = 9
UInt64 = 11