There is no diffrence between string and String. string is a alias created by microsoft for System.string.There are some other datatypes for which microsoft has created the alias.These are the aliases defined:string->System.Stringsbyte->System.SBytebyte->System.Byteshort->System.Int16ushort->System.UInt16int->System.Int32uint->System.UInt32long->System.Int64ulong->System.UInt64char->System.Charfloat->System.Singledouble->System.Doublebool->System.Boolean
decimal->System.Decimal