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.