Random Constructor (Int32)
Initializes a new instance of the Random class, using the specified seed value.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
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.
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.
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
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 constructor and seed parameter.
// Example of the Random class constructors and Random.NextDouble( ) // method. 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( 1 ); Console.WriteLine( "\nRandom numbers from a Random object " + "with an auto-generated seed:" ); Random autoRand = new Random( ); RunIntNDoubleRandoms( autoRand ); } static void Main( ) { Console.WriteLine( "This example of the Random class constructors and " + "Random.NextDouble( ) \n" + "generates 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: 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 */
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.
