Random Constructor (Int32) (System)

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Random Constructor (Int32)

Updated: January 2012

Initializes a new instance of the Random class, using the specified seed value.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Visual Basic
Public Sub New ( _
	Seed As Integer _
)
C#
public Random(
	int Seed
)
Visual C++
public:
Random(
	int Seed
)
F#
new : 
        Seed:int -> Random

Parameters

Seed
Type: System.Int32
A number used to calculate a starting value for the pseudo-random number sequence. If a negative number is specified, the absolute value of the number is used.
Remarks

Providing an identical seed value to different Random objects causes each instance to produce identical sequences of random numbers.

If your application requires different random number sequences, invoke this constructor repeatedly with different seed values. One way to produce a unique seed value is to make it time-dependent. For example, derive the seed value from the system clock. However, the system clock might not have sufficient resolution to provide different invocations of this constructor with a different seed value. This results in random number generators that generate identical sequences of pseudo-random numbers, as illustrated by the first two Random objects in the following example. To prevent this, apply an algorithm to differentiate the seed value in each invocation, or call the Thread.Sleep method to ensure that you provide each constructor with a different seed value.

Visual Basic

Imports System.Threading

Module RandomNumbers
   Public Sub Main()
      Dim rand1 As New Random(CInt(Date.Now.Ticks And &h0000FFFF))
      Dim rand2 As New Random(CInt(Date.Now.Ticks And &h0000FFFF))
      Thread.Sleep(20)
      Dim rand3 As New Random(CInt(Date.Now.Ticks And &h0000FFFF))
      ShowRandomNumbers(rand1)
      ShowRandomNumbers(rand2)
      ShowRandomNumbers(rand3)
   End Sub

   Private Sub ShowRandomNumbers(rand As Random)
      Console.WriteLine()
      Dim values(4) As Byte
      rand.NextBytes(values)
      For Each value As Byte In values
         Console.Write("{0, 5}", value)
      Next      
      Console.WriteLine() 
   End Sub
End Module
' The example displays output similar to the following:
'      145  214  177  134  173
'    
'      145  214  177  134  173
'    
'      126  185  175  249  157
C#

using System;
using System.Threading;

public class Example
{
   public static void Main()
   {
      Random rand1 = new Random((int) DateTime.Now.Ticks & 0x0000FFFF);
      Random rand2 = new Random((int) DateTime.Now.Ticks & 0x0000FFFF);
      Thread.Sleep(20);
      Random rand3 = new Random((int) DateTime.Now.Ticks & 0x0000FFFF);
      ShowRandomNumbers(rand1);
      ShowRandomNumbers(rand2);
      ShowRandomNumbers(rand3);
   }

   private static void ShowRandomNumbers(Random rand)
   {
      Console.WriteLine();
      byte[] values = new byte[4];
      rand.NextBytes(values);
      foreach (var value in values)
         Console.Write("{0, 5}", value);

      Console.WriteLine(); 
   }
}
// The example displays output similar to the following:
//   145  214  177  134  173
// 
//   145  214  177  134  173
// 
//   126  185  175  249  157
Examples

The following example creates Random objects with the class constructor that takes a seed parameter and generates a sequence of random integers and doubles. The example illustrates that the same sequence is generated when the Random object is created again with the same seed parameter.

Visual Basic

Imports System.Threading

Module RandomObjectDemo
    ' Generate random numbers from the specified Random object.
    Sub RunIntNDoubleRandoms(randObj As Random)

        ' Generate the first six random integers.
        Dim j As Integer
        For j = 0 To 5
            Console.Write(" {0,10} ", randObj.Next())
        Next j
        Console.WriteLine()

        ' Generate the first six random doubles.
        For j = 0 To 5
            Console.Write(" {0:F8} ", randObj.NextDouble())
        Next j
        Console.WriteLine()
    End Sub 

    ' Create a Random object with the specified seed.
    Sub FixedSeedRandoms(seed As Integer)
        Console.WriteLine(vbCrLf & _
            "Random numbers from a Random object with seed = {0}:", 
            seed)
        Dim fixRand As New Random(seed)

        RunIntNDoubleRandoms(fixRand)
    End Sub 

    ' Create a random object with a timer-generated seed.
    Sub AutoSeedRandoms()
        ' Wait to allow the timer to advance.
        Thread.Sleep(20)

        Console.WriteLine(vbCrLf & _
            "Random numbers from a Random object with an auto-generated seed:")
        Dim autoRand As New Random()

        RunIntNDoubleRandoms(autoRand)
    End Sub 

    Sub Main()
        FixedSeedRandoms(123)
        FixedSeedRandoms(123)

        FixedSeedRandoms(456)
        FixedSeedRandoms(456)

        AutoSeedRandoms()
        AutoSeedRandoms()
        AutoSeedRandoms()
    End Sub
End Module 
' 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
C#

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
Visual C++

// Example of the Random class constructors and Random::NextDouble( ) 
// method.
using namespace System;
using namespace System::Threading;

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


// Create a random object with a timer-generated seed.
void AutoSeedRandoms()
{

   // Wait to allow the timer to advance.
   Thread::Sleep( 1 );
   Console::WriteLine( "\nRandom numbers from a Random object "
   "with an auto-generated seed:" );
   Random^ autoRand = gcnew Random;
   RunIntNDoubleRandoms( autoRand );
}

int main()
{
   Console::WriteLine( "This example of the Random class constructors and Random"
   "::NextDouble( ) \ngenerates the following output.\n" );
   Console::WriteLine( "Create Random objects, and then generate and "
   "display six integers and \nsix doubles from each." );
   FixedSeedRandoms( 123 );
   FixedSeedRandoms( 123 );
   FixedSeedRandoms( 456 );
   FixedSeedRandoms( 456 );
   AutoSeedRandoms();
   AutoSeedRandoms();
   AutoSeedRandoms();
}

/*
This example of the Random class constructors and Random::NextDouble( )
generates the following output.

Create Random objects, and then generate and display six integers and
six doubles from each.

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:
 1624372556  1894939458   302472229   588108304    23919954  1085111949
 0.14595512  0.30162298  0.92267372  0.55707657  0.25430079  0.74143239

Random numbers from a Random object with an auto-generated seed:
 2105952511  1753605347   280739490   876793040  1129567796   524571616
 0.62652210  0.31846701  0.15984073  0.24458755  0.62160607  0.54857684

Random numbers from a Random object with an auto-generated seed:
  440048819  1612271236   259006751  1165477776    87731991  2111514930
 0.10708907  0.33531104  0.39700773  0.93209853  0.98891135  0.35572129
*/
Version Information

.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
Platforms

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.
See Also

Reference

Random Class
Random Overload
System Namespace
Change History

Date

History

Reason

January 2012

Replaced the example.

Customer feedback.