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Random.NextDouble Method

Returns a random number between 0.0 and 1.0.

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

public virtual double NextDouble()

Return Value

Type: System.Double
A double-precision floating point number greater than or equal to 0.0, and less than 1.0.

This method is the public version of the protected method, Sample.

The following example uses the NextDouble method to generate sequences of random doubles.


using System;
using System.Threading;

public class RandomObjectDemo  
{
    // Generate random numbers from the specified Random object.
    static void RunIntNDoubleRandoms( Random randObj )
    {
        // Generate the first six random integers.
        for( int j = 0; j < 6; j++ )
            Console.Write(" {0,10} ", randObj.Next());
        Console.WriteLine();

        // Generate the first six random doubles.
        for( int j = 0; j < 6; j++ )
            Console.Write(" {0:F8} ", randObj.NextDouble( ) );
        Console.WriteLine();
    }

    // Create a Random object with the specified seed.
    static void FixedSeedRandoms(int seed)
    {
        Console.WriteLine( 
            "\nRandom numbers from a Random object with seed = {0}:", 
            seed );
        Random fixRand = new Random(seed);
        RunIntNDoubleRandoms(fixRand);
    }

    // Create a random object with a timer-generated seed.
    static void AutoSeedRandoms()
    {
        // Wait to allow the timer to advance.
        Thread.Sleep(20);

        Console.WriteLine( 
            "\nRandom numbers from a Random object with an auto-generated seed:");
        Random autoRand = new Random();
        RunIntNDoubleRandoms(autoRand);
    }

    static void Main()
    {	
        FixedSeedRandoms(123);
        FixedSeedRandoms(123);

        FixedSeedRandoms(456);
        FixedSeedRandoms(456);

        AutoSeedRandoms();
        AutoSeedRandoms();
        AutoSeedRandoms();
    }
}
// This example displays output similar to the following:
//    Random numbers from a Random object with seed = 123:
//     2114319875  1949518561  1596751841  1742987178  1586516133   103755708
//     0.01700087  0.14935942  0.19470390  0.63008947  0.90976122  0.49519146
//    
//    Random numbers from a Random object with seed = 123:
//     2114319875  1949518561  1596751841  1742987178  1586516133   103755708
//     0.01700087  0.14935942  0.19470390  0.63008947  0.90976122  0.49519146
//    
//    Random numbers from a Random object with seed = 456:
//     2044805024  1323311594  1087799997  1907260840   179380355   120870348
//     0.21988117  0.21026556  0.39236514  0.42420498  0.24102703  0.47310170
//    
//    Random numbers from a Random object with seed = 456:
//     2044805024  1323311594  1087799997  1907260840   179380355   120870348
//     0.21988117  0.21026556  0.39236514  0.42420498  0.24102703  0.47310170
//    
//    Random numbers from a Random object with an auto-generated seed:
//     1005316318   212129543  1298121862    15554380   287332403  1482179893
//     0.54097964  0.57722251  0.26063171  0.74283980  0.86753811  0.35308197
//    
//    Random numbers from a Random object with an auto-generated seed:
//     1775844246  1703981883  1692846203   906946687   767878762  1444308819
//     0.70988680  0.60417296  0.24009892  0.64285736  0.65522655  0.84451309
//    
//    Random numbers from a Random object with an auto-generated seed:
//      398888527  1048350576  2087570550  1798338994  1248425121  1406437745
//     0.87879396  0.63112340  0.21956613  0.54287493  0.44291500  0.33594421


The following example calls the NextDouble method to generate 100 random numbers and displays their frequency distribution.


using System;

public class Example
{
   public static void Main()
   {
      int[] frequency = new int[10];
      double number;
      Random rnd = new Random();

      for (int ctr = 0; ctr <= 99; ctr++) {
         number = rnd.NextDouble();
         frequency[(int) Math.Floor(number*10)] ++;
      }
      Console.WriteLine("Distribution of Random Numbers:");
      for (int ctr = frequency.GetLowerBound(0); ctr <= frequency.GetUpperBound(0); ctr++)
         Console.WriteLine("0.{0}0-0.{0}9       {1}", ctr, frequency[ctr]);
   }
}
// The following example displays output similar to the following:
//       Distribution of Random Numbers:
//       0.00-0.09       16
//       0.10-0.19       8
//       0.20-0.29       8
//       0.30-0.39       11
//       0.40-0.49       9
//       0.50-0.59       6
//       0.60-0.69       13
//       0.70-0.79       6
//       0.80-0.89       9
//       0.90-0.99       14


.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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