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Random Constructor (Int32)

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

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

Syntax

'Declaration
Public Sub New ( _
    Seed As Integer _
)

public Random(
    int Seed
)

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.

Exceptions

Exception Condition
OverflowException

Seed is Int32.MinValue, which causes an overflow when its absolute value is calculated.

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. In that case, apply an algorithm to differentiate the seed value in each invocation. For example, the following code uses the right-shift operator to generate different seed values for a number of Random objects (between 1 and approximately 28 objects) that might be initialized with the same time value.

Imports System.Threading

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim rand1 As New Random()
      Dim rand2 As New Random()
      Thread.Sleep(2000)
      Dim rand3 As New Random()
      ShowExample(outputBlock, rand1)
      ShowExample(outputBlock, rand2)
      ShowExample(outputBlock, rand3)
   End Sub

   Private Sub ShowExample(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal rand As Random)
      outputBlock.Text &= vbCrLf
      Dim values(4) As Byte
      rand.NextBytes(values)
      For Each value As Byte In values
         outputBlock.Text += String.Format("{0, 5}", value)
      Next
      outputBlock.Text &= vbCrLf
   End Sub
End Module
' The example displays the following output:
'       28   35  133  224   58
'    
'       28   35  133  224   58
'    
'       32  222   43  251   49

using System;
using System.Threading;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Random rand1 = new Random();
      Random rand2 = new Random();
      Thread.Sleep(2000);
      Random rand3 = new Random();
      ShowExample(outputBlock, rand1);
      ShowExample(outputBlock, rand2);
      ShowExample(outputBlock, rand3);
   }

   private static void ShowExample(System.Windows.Controls.TextBlock outputBlock, Random rand)
   {
      outputBlock.Text += "\n";
      byte[] values = new byte[5];
      rand.NextBytes(values);
      foreach (byte value in values)
         outputBlock.Text += String.Format("{0, 5}", value);
      outputBlock.Text += "\n";
   }
}
// The example displays the following output:
//       28   35  133  224   58
//    
//       28   35  133  224   58
//    
//       32  222   43  251   49

Examples

The following code 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 constructor and seed parameter.

' Example of the Random class constructors and Random.NextDouble( ) 
' method.
Imports System.Threading

Module Example
   ' Generate random numbers from the specified Random object.
   Sub RunIntNDoubleRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock, _
                            ByVal randObj As Random)

      ' Generate the first six random integers.
      Dim j As Integer
      For j = 0 To 5
         outputBlock.Text &= String.Format(" {0,10} ", randObj.Next())
      Next j
      outputBlock.Text &= vbCrLf

      ' Generate the first six random doubles.
      For j = 0 To 5
         outputBlock.Text &= String.Format(" {0:F8} ", randObj.NextDouble())
      Next j
      outputBlock.Text &= vbCrLf
   End Sub

   ' Create a Random object with the specified seed.
   Sub FixedSeedRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal seed As Integer)

      outputBlock.Text &= String.Format(vbCrLf & _
          "Random numbers from a Random object with " & _
          "seed = {0}:", seed) & vbCrLf
      Dim fixRand As New Random(seed)

      RunIntNDoubleRandoms(outputBlock, fixRand)
   End Sub

   ' Create a random object with a timer-generated seed.
   Sub AutoSeedRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Wait to allow the timer to advance.
      Thread.Sleep(1)

      outputBlock.Text &= String.Format(vbCrLf & _
          "Random numbers from a Random object " & _
          "with an auto-generated seed:") & vbCrLf
      Dim autoRand As New Random()

      RunIntNDoubleRandoms(outputBlock, autoRand)
   End Sub

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      outputBlock.Text &= String.Format( _
          "This example of the Random class constructors " & _
          "and Random.NextDouble( ) " & vbCrLf & _
          "generates the following output." & vbCrLf) & vbCrLf
      outputBlock.Text &= String.Format("Create Random " & _
          "objects, and then generate and display six " & _
          "integers and " & vbCrLf & "six doubles from each.") & vbCrLf

      FixedSeedRandoms(outputBlock, 123)
      FixedSeedRandoms(outputBlock, 123)

      FixedSeedRandoms(outputBlock, 456)
      FixedSeedRandoms(outputBlock, 456)

      AutoSeedRandoms(outputBlock)
      AutoSeedRandoms(outputBlock)
      AutoSeedRandoms(outputBlock)
   End Sub
End Module

' 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:
'  1920831619  1346865774  2006582766  1968819760   332463652   110770792
'  0.71326689  0.50383335  0.50446082  0.66312569  0.94517193  0.58059287
' 
' Random numbers from a Random object with an auto-generated seed:
'   254927927  1205531663  1984850027   110020849  1438111494  1697714106
'  0.19383387  0.52067738  0.74162783  0.35063667  0.31247720  0.38773733
' 
' Random numbers from a Random object with an auto-generated seed:
'   736507882  1064197552  1963117288   398705585   396275689  1137173773
'  0.67440084  0.53752140  0.97879483  0.03814764  0.67978248  0.19488178

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

public class Example
{
   // Generate random numbers from the specified Random object.
   static void RunIntNDoubleRandoms(System.Windows.Controls.TextBlock outputBlock, Random randObj)
   {
      // Generate the first six random integers.
      for (int j = 0; j < 6; j++)
         outputBlock.Text += String.Format(" {0,10} ", randObj.Next());
      outputBlock.Text += "\n";

      // Generate the first six random doubles.
      for (int j = 0; j < 6; j++)
         outputBlock.Text += String.Format(" {0:F8} ", randObj.NextDouble());
      outputBlock.Text += "\n";
   }

   // Create a Random object with the specified seed.
   static void FixedSeedRandoms(System.Windows.Controls.TextBlock outputBlock, int seed)
   {
      outputBlock.Text += String.Format(
          "\nRandom numbers from a Random object with " +
          "seed = {0}:", seed) + "\n";
      Random fixRand = new Random(seed);

      RunIntNDoubleRandoms(outputBlock, fixRand);
   }

   // Create a random object with a timer-generated seed.
   static void AutoSeedRandoms(System.Windows.Controls.TextBlock outputBlock)
   {
      // Wait to allow the timer to advance.
      Thread.Sleep(1);

      outputBlock.Text += String.Format(
          "\nRandom numbers from a Random object " +
          "with an auto-generated seed:") + "\n";
      Random autoRand = new Random();

      RunIntNDoubleRandoms(outputBlock, autoRand);
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      outputBlock.Text += String.Format(
          "This example of the Random class constructors and " +
          "Random.NextDouble( ) \n" +
          "generates the following output.\n") + "\n";
      outputBlock.Text += String.Format(
          "Create Random objects, and then generate and " +
          "display six integers and \nsix doubles from each.") + "\n";

      FixedSeedRandoms(outputBlock, 123);
      FixedSeedRandoms(outputBlock, 123);

      FixedSeedRandoms(outputBlock, 456);
      FixedSeedRandoms(outputBlock, 456);

      AutoSeedRandoms(outputBlock);
      AutoSeedRandoms(outputBlock);
      AutoSeedRandoms(outputBlock);
   }
}

/*
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:
  380213349   127379247  1969091178  1983029819  1963098450  1648433124
 0.08824121  0.41249688  0.36445811  0.05637512  0.62702451  0.49595560

Random numbers from a Random object with an auto-generated seed:
  861793304  2133528783  1947358439   124230908   921262645  1087892791
 0.56880819  0.42934091  0.60162512  0.74388610  0.99432979  0.30310005

Random numbers from a Random object with an auto-generated seed:
 1343373259  1992194672  1925625700   412915644  2026910487   527352458
 0.04937517  0.44618494  0.83879212  0.43139707  0.36163507  0.11024451
*/

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.