C#产生不重复随机数

static int GetRandomSeed( ) 
{ 
byte[] bytes = new byte[4]; 
System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider( ); 
rng.GetBytes( bytes ); 
return BitConverter.ToInt32( bytes , 0 ); 
} 

Random random = new Random( GetRandomSeed( ) );