C Sharp TutorialC Sharp .NET Compiler Platform (Roslyn)C Sharp 3.0 FeaturesC Sharp 4.0 FeaturesC Sharp 5.0 FeaturesC Sharp 6.0 FeaturesC Sharp 7.0 FeaturesC Sharp Access ModifiersC Sharp Access network shared folder with username and passwordC Sharp Accessing DatabasesC Sharp Action FiltersC Sharp Aliases of built-in typesC Sharp an overview of collectionsC Sharp Anonymous typesC Sharp ArraysC Sharp ASP.NET IdentityC Sharp AssemblyInfo.cs ExamplesC Sharp Async-AwaitC Sharp Async/await, Backgroundworker, Task and Thread ExamplesC Sharp Asynchronous SocketC Sharp AttributesC Sharp Authentication handlerC Sharp BackgroundWorkerC Sharp BigIntegerC Sharp Binary SerializationC Sharp BindingListC Sharp Built-in TypesC Sharp CachingC Sharp CastingC Sharp Checked and UncheckedC Sharp CLSCompliantAttributeC Sharp Code ContractsC Sharp Code Contracts and AssertionsC Sharp Collection InitializersC Sharp Comments and regionsC Sharp Common String OperationsC Sharp Conditional StatementsC Sharp Constructors and FinalizersC Sharp Creating Own MessageBox in Windows Form ApplicationC Sharp Creational Design PatternsC Sharp Cryptography (System.Security.Cryptography)C Sharp Data AnnotationC Sharp DateTime MethodsC Sharp DelegatesC Sharp Dependency InjectionC Sharp DiagnosticsC Sharp Dynamic typeC Sharp EnumC Sharp Equality OperatorC Sharp Equals and GetHashCodeC Sharp EventsC Sharp Exception HandlingC Sharp Expression TreesC Sharp Extension MethodsC Sharp File and Stream I/OC Sharp FileSystemWatcherC Sharp Func delegatesC Sharp Function with multiple return valuesC Sharp Functional ProgrammingC Sharp Garbage Collector in .NETC Sharp Generating Random NumbersC Sharp Generic Lambda Query BuilderC Sharp GenericsC Sharp Getting Started: Json with C SharpC Sharp GuidC Sharp Handling FormatException when converting string to other typesC Sharp Hash FunctionsC Sharp ICloneableC Sharp IComparableC Sharp IDisposable interfaceC Sharp IEnumerableC Sharp ILGeneratorC Sharp ImmutabilityC Sharp Implementing Decorator Design PatternC Sharp Implementing Flyweight Design PatternC Sharp Import Google ContactsC Sharp Including Font ResourcesC Sharp IndexerC Sharp InheritanceC Sharp Initializing PropertiesC Sharp INotifyPropertyChanged interfaceC Sharp InterfacesC Sharp InteroperabilityC Sharp IQueryable interfaceC Sharp IteratorsC Sharp KeywordsC Sharp Lambda expressionsC Sharp Lambda ExpressionsC Sharp LINQ QueriesC Sharp LINQ to Objects

C Sharp Generating Random Numbers

From WikiOD

Syntax[edit | edit source]

  • Random()
  • Random(int Seed)
  • int Next()
  • int Next(int maxValue)
  • int Next(int minValue, int maxValue)

Parameters[edit | edit source]

Parameters Details
Seed A value for generating random numbers. If not set, the default value is determined by the current system time.
minValue Generated numbers won't be smaller than this value. If not set, the default value is 0.
maxValue Generated numbers will be smaller than this value. If not set, the default value is Int32.MaxValue.
return value Returns a number with random value.

Remarks[edit | edit source]

The random seed generated by the system isn't the same in every different run.

Seeds generated in the same time might be the same.

Generate a random int[edit | edit source]

This example generates random values between 0 and 2147483647.

Random rnd = new Random();
int randomNumber = rnd.Next();

Generate a random int in a given range[edit | edit source]

Generate a random number between minValue and maxValue - 1.

Random rnd = new Random();
var randomBetween10And20 = rnd.Next(10, 20);

Generating the same sequence of random numbers over and over again[edit | edit source]

When creating Random instances with the same seed, the same numbers will be generated.

int seed = 5;
for (int i = 0; i < 2; i++)
   Console.WriteLine("Random instance " + i);
   Random rnd = new Random(seed);
   for (int j = 0; j < 5; j++)
      Console.Write(" ");



Random instance 0
726643700 610783965 564707973 1342984399 995276750
Random instance 1
726643700 610783965 564707973 1342984399 995276750

Create multiple random class with different seeds simultaneously[edit | edit source]

Two Random class created at the same time will have the same seed value.

Using System.Guid.NewGuid().GetHashCode() can get a different seed even in the same time.

Random rnd1 = new Random();
Random rnd2 = new Random();
Console.WriteLine("First 5 random number in rnd1");
for (int i = 0; i < 5; i++)

Console.WriteLine("First 5 random number in rnd2");
for (int i = 0; i < 5; i++)

rnd1 = new Random(Guid.NewGuid().GetHashCode());
rnd2 = new Random(Guid.NewGuid().GetHashCode());
Console.WriteLine("First 5 random number in rnd1 using Guid");
for (int i = 0; i < 5; i++)
Console.WriteLine("First 5 random number in rnd2 using Guid");
for (int i = 0; i < 5; i++)

Another way to achieve different seeds is to use another Random instance to retrieve the seed values.

Random rndSeeds = new Random();
Random rnd1 = new Random(rndSeeds.Next());
Random rnd2 = new Random(rndSeeds.Next());

This also makes it possible to control the result of all the Random instances by setting only the seed value for the rndSeeds. All the other instances will be deterministically derived from that single seed value.

Generate a Random double[edit | edit source]

Generate a random number between 0 and 1.0. (not including 1.0)

Random rnd = new Random();
var randomDouble = rnd.NextDouble();

Generate a random character[edit | edit source]

Generate a random letter between a and z by using the Next() overload for a given range of numbers, then converting the resulting int to a char

Random rnd = new Random();
char randomChar = (char)rnd.Next('a','z'); 
//'a' and 'z' are interpreted as ints for parameters for Next()

Generate a number that is a percentage of a max value[edit | edit source]

A common need for random numbers it to generate a number that is X% of some max value. this can be done by treating the result of NextDouble() as a percentage:

var rnd = new Random();
var maxValue = 5000;
var percentage = rnd.NextDouble();
var result = maxValue * percentage; 
//suppose NextDouble() returns .65, result will hold 65% of 5000: 3250.