What is diffrence between string and String in C#.net

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.String

sbyte->System.SByte

byte->System.Byte

short->System.Int16

ushort->System.UInt16

int->System.Int32

uint->System.UInt32

long->System.Int64

ulong->System.UInt64

char->System.Char

float->System.Single

double->System.Double

bool->System.Boolean

decimal->System.Decimal