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RNGCryptoServiceProvider Class

Implements a cryptographic Random Number Generator (RNG) using the implementation provided by the cryptographic service provider (CSP). This class cannot be inherited.

System.Object
  System.Security.Cryptography.RandomNumberGenerator
    System.Security.Cryptography.RNGCryptoServiceProvider

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

[ComVisibleAttribute(true)]
public sealed class RNGCryptoServiceProvider : RandomNumberGenerator

The RNGCryptoServiceProvider type exposes the following members.

  NameDescription
Public methodRNGCryptoServiceProvider()Initializes a new instance of the RNGCryptoServiceProvider class.
Public methodRNGCryptoServiceProvider(Byte[])Initializes a new instance of the RNGCryptoServiceProvider class.
Public methodRNGCryptoServiceProvider(CspParameters)Initializes a new instance of the RNGCryptoServiceProvider class with the specified parameters.
Public methodRNGCryptoServiceProvider(String)Initializes a new instance of the RNGCryptoServiceProvider class.
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  NameDescription
Public methodDispose()When overridden in a derived class, releases all resources used by the current instance of the RandomNumberGenerator class. (Inherited from RandomNumberGenerator.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodGetBytes(Byte[])Fills an array of bytes with a cryptographically strong sequence of random values. (Overrides RandomNumberGenerator.GetBytes(Byte[]).)
Public methodGetBytes(Byte[], Int32, Int32)Fills the specified byte array with a cryptographically strong random sequence of values. (Inherited from RandomNumberGenerator.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetNonZeroBytesFills an array of bytes with a cryptographically strong sequence of random nonzero values. (Overrides RandomNumberGenerator.GetNonZeroBytes(Byte[]).)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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Important noteImportant

This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable” section in the IDisposable interface topic.

The following code example shows how to create a random number with the RNGCryptoServiceProvider class.

//The following sample uses the Cryptography class to simulate the roll of a dice. 

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

class RNGCSP
{
    private static RNGCryptoServiceProvider rngCsp = new RNGCryptoServiceProvider();
    // Main method. 
    public static void Main()
    {
        const int totalRolls = 25000;
        int[] results = new int[6];

        // Roll the dice 25000 times and display 
        // the results to the console. 
        for (int x = 0; x < totalRolls; x++)
        {
            byte roll = RollDice((byte)results.Length);
            results[roll - 1]++;
        }
        for (int i = 0; i < results.Length; ++i)
        {
            Console.WriteLine("{0}: {1} ({2:p1})", i + 1, results[i], (double)results[i] / (double)totalRolls);
        }
        rngCsp.Dispose();
        Console.ReadLine();
    }

    // This method simulates a roll of the dice. The input parameter is the 
    // number of sides of the dice. 

    public static byte RollDice(byte numberSides)
    {
        if (numberSides <= 0)
            throw new ArgumentOutOfRangeException("numberSides");

        // Create a byte array to hold the random value. 
        byte[] randomNumber = new byte[1];
        do
        {
            // Fill the array with a random value.
            rngCsp.GetBytes(randomNumber);
        }
        while (!IsFairRoll(randomNumber[0], numberSides));
        // Return the random number mod the number 
        // of sides.  The possible values are zero- 
        // based, so we add one. 
        return (byte)((randomNumber[0] % numberSides) + 1);
    }

    private static bool IsFairRoll(byte roll, byte numSides)
    {
        // There are MaxValue / numSides full sets of numbers that can come up 
        // in a single byte.  For instance, if we have a 6 sided die, there are 
        // 42 full sets of 1-6 that come up.  The 43rd set is incomplete. 
        int fullSetsOfValues = Byte.MaxValue / numSides;

        // If the roll is within this range of fair values, then we let it continue. 
        // In the 6 sided die case, a roll between 0 and 251 is allowed.  (We use 
        // < rather than <= since the = portion allows through an extra 0 value). 
        // 252 through 255 would provide an extra 0, 1, 2, 3 so they are not fair 
        // to use. 
        return roll < numSides * fullSetsOfValues;
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

This type is thread safe.

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