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Random Constructor (Int32)

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

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

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.

ExceptionCondition
OverflowException

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

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.


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


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.
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
*/


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

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

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