Random number generator in C#

Question

I don't know if it is any good. I've never done this, thus, I noticed it is kinda slow.

Can you suggest improvements? I may use it in actual software in the future.

private int secgen(int minvalue, int maxvalue)
 {
 Func<int, int, int, int> modular = (a, b, mod) => 
 {
 long rem;
 Math.DivRem((long)a + (long)b, (long)mod, out rem);
 if (rem < minvalue)
 rem += minvalue;
 return (int)rem;
 };
 byte[] entropyBytes = new byte[257];
 RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
 rng.GetBytes(entropyBytes);
 int value = entropyBytes[0];
 for (int i = 1; i < 257; i++) 
 {
 value = modular(value, entropyBytes[i], maxvalue);
 }
 //MessageBox.Show(value.ToString());
 return value;
 }

• Denis: What do you need the random numbers for ?
• craftworkgames: "good" has different meanings when it comes to random number generators. Uniformity, Independence, Replication, Cycle length, Speed, Memory usage, etc. Depends what you're going for.
• JanDotNet: The algorithm does not work correct: For instance: MinValue: 10000 and MaxValue: 10010 produces values like: 18752, 19675, ....
• looseblank: @JanDotNet Thanks for catching that. I used a lazy method adding MinValue to the remainder

Answer 1

You may improve performance:

I would use the modulo operator instead of a function call you aren't benefiting from 100%. Math.DivRem returns a value (quotient) that you don't use. Same result:

var rem = a + b % mod;

Saves you a few unboxing operations and method call

Func<int, int, int, int> modular = (a, b, mod) =>
{
 var rem = a + b % mod;
 if (rem < minvalue)
 rem += minvalue;
 return rem;
};

Saves half the time? http://pastebin.com/XTaLCQh4

• looseblank: Thanks, I've always had trouble finding the right operators in the language.