Random Class
Represents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness.
For a list of all members of this type, see Random Members.
System.Object
System.Random
[Visual Basic] <Serializable> Public Class Random [C#] [Serializable] public class Random [C++] [Serializable] public __gc class Random [JScript] public Serializable class Random
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Remarks
Pseudo-random numbers are chosen with equal probability from a finite set of numbers. The chosen numbers are not completely random because a definite mathematical algorithm is used to select them, but they are sufficiently random for practical purposes.
The random number generation starts from a seed value. If the same seed is used repeatedly, the same series of numbers is generated. One way to produce different sequences is to make the seed value time-dependent, thereby producing a different series with each new instance of Random.
To improve performance, create one Random to generate many random numbers over time, instead of repeatedly creating a new Random to generate one random number.
To generate a cryptographically secure random number suitable for creating a random password, for example, use a class derived from System.Security.Cryptography.RandomNumberGenerator such as System.Security.Cryptography.RNGCryptoServiceProvider.
Example
[Visual Basic, C#, C++] The following code example creates Random objects with different overloads of the class constructor and generates sequences of random Int32 and Double values from the objects.
[Visual Basic] ' Example of the Random class constructors and Random.NextDouble( ) ' method. Imports System Imports System.Threading Imports Microsoft.VisualBasic 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( 1 ) 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( ) Console.WriteLine( _ "This example of the Random class constructors " & _ "and Random.NextDouble( ) " & vbCrLf & _ "generates the following output." & vbCrLf ) Console.WriteLine( "Create Random " & _ "objects, and then generate and display six " & _ "integers and " & vbCrLf & "six doubles from each." ) FixedSeedRandoms( 123 ) FixedSeedRandoms( 123 ) FixedSeedRandoms( 456 ) FixedSeedRandoms( 456 ) AutoSeedRandoms( ) AutoSeedRandoms( ) AutoSeedRandoms( ) 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 [C#] // 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 */ [C++] // Example of the Random class constructors and Random::NextDouble( ) // method. #using <mscorlib.dll> 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( S" {0,10} ", __box( randObj->Next( ) ) ); Console::WriteLine( ); // Generate the first six random doubles. for( int j = 0; j < 6; j++ ) Console::Write( S" {0:F8} ", __box( randObj->NextDouble( ) ) ); Console::WriteLine( ); } // Create a Random object with the specified seed. void FixedSeedRandoms( int seed ) { Console::WriteLine( S"\nRandom numbers from a Random object with seed = {0}:", __box( seed ) ); Random* fixRand = new 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( S"\nRandom numbers from a Random object " S"with an auto-generated seed:" ); Random* autoRand = new Random( ); RunIntNDoubleRandoms( autoRand ); } void main( ) { Console::WriteLine( S"This example of the Random class constructors and Random" S"::NextDouble( ) \ngenerates the following output.\n" ); Console::WriteLine( S"Create Random objects, and then generate and " S"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 */
[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button
in the upper-left corner of the page.
Requirements
Namespace: System
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework
Assembly: Mscorlib (in Mscorlib.dll)