How to Generate Random Number And Random String In C#?

C# Random class provides functionality Implements to generate random number in C# step by step. The Random class constructors have two main overloaded forms. It takes either no data value or it takes a some seed value.

• Random.Next() -> returns a random number
• Random.NextBytes() -> returns an array of bytes filled with random numbers
• Random.NextDouble() -> returns a random number between 0.0 and 1.0.

also You can read my Prev Article For C# Dynamic Data Type

C# Random Number And C# Random String Generator With Code Examples

The Random class provides Random.Next(), Random.NextBytes(), and Random.NextDouble() methods. The Random.Next() method returns a random number, Random.NextBytes() returns an array of bytes filled with random numbers, and Random.NextDouble() returns a random number between 0.0 and 1.0(c# random double).

The Random.Next() method has main 3 overloaded forms as well as allows you to set & get the minimum as well as maximum range of the fetch random number.

The following below source code returns a random number.

int num = random.Next(); 

c# random number between 1 and 100 for user define Function

static int RandomNumber(int min, int max)
{
    Random random = new Random(); return random.Next(min, max);

}

Random integer between 0 and 100(100 not included):

Random random = new Random();
int randomNumber = random.Next(0, 100);

The following simple syntax code returns a random number less than 5000.

int num = random.Next(5000);  

The following simple c# Source code returns a random number between the min as well as the max range.

// Generate a random number between two numbers  
public int RandomNumber(int min, int max)  
{  
    Random random = new Random();  
    return random.Next(min, max);  
}  

You can even merge the two simple methods -first is a RandomNumber and second is a RandomString to generate a combination of get a random string and numbers.

// Generate a random string with a given size  
public string RandomString(int size, bool lowerCase)  
{  
    StringBuilder builder = new StringBuilder();  
    Random random = new Random();  
    char ch;  
    for (int i = 0; i < size; i++)  
    {  
        ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));  
        builder.Append(ch);  
    }  
    if (lowerCase)  
        return builder.ToString().ToLower();  
    return builder.ToString();  
}  

The following below source code generates a password of total length of the 10 with first 4 letters lowercase, next 4 letters numbers, as well as last 2 letters as uppercase.

// Generate a random password  
public string RandomPassword()  
{  
    StringBuilder builder = new StringBuilder();  
    builder.Append(RandomString(4, true));  
    builder.Append(RandomNumber(1000, 9999));  
    builder.Append(RandomString(2, false));  
    return builder.ToString();  
}  

Example : c# generate random number

Here is the full source code written in .NET Core 2.0 c# random integer.

using System;    
using System.Text;    
    
class RandomNumberSample    
{    
    static void Main(string[] args)    
    {   
        RandomGenerator generator = new RandomGenerator();    
        int rand = generator.RandomNumber(5, 100);    
        Console.WriteLine($"Random number between 5 and 100 is {rand}");    
    
        string str = generator.RandomString(10, false);    
        Console.WriteLine($"Random string of 10 chars is {str}");    
    
        string pass = generator.RandomPassword();    
        Console.WriteLine($"Random string of 6 chars is {pass}");    
    
        Console.ReadKey();    
    }    
}    
    
public class RandomGenerator    
{    
    // Generate a random number between two numbers    
    public int RandomNumber(int min, int max)    
    {    
        Random random = new Random();    
        return random.Next(min, max);    
    }    
    
    // Generate a random string with a given size    
    public string RandomString(int size, bool lowerCase)    
    {    
        StringBuilder builder = new StringBuilder();    
        Random random = new Random();    
        char ch;    
        for (int i = 0; i < size; i++)    
        {    
            ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));    
            builder.Append(ch);    
        }    
        if (lowerCase)    
            return builder.ToString().ToLower();    
        return builder.ToString();    
    }    
    
    // Generate a random password    
    public string RandomPassword()    
    {    
        StringBuilder builder = new StringBuilder();    
        builder.Append(RandomString(4, true));    
        builder.Append(RandomNumber(1000, 9999));    
        builder.Append(RandomString(2, false));    
        return builder.ToString();    
    }    
}   

The best output from above full source code c# random number generator is shown in Screen Shot 1.

Ref. Random.Next Method

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