C# Bogus

last modified July 5, 2023

In this article we show how to generate fake data in C# using the Bogus library.

Bogus is a simple fake data generator for .NET. It is inspired by faker.js.

Fake data is useful when building and testing our application.

We can use a classic, procedural or a fluent syntax to generate fake data.

$ dotnet add package Bogus

Inside a project, we add the Bogus package.

C# Bogus simple example

The following is a simple example that generates fake data.

Program.cs

using Bogus;

var occupations = new string[] { “gardener”, “teacher”, “writer”, “programmer” }; var faker = new Faker<User>() .RuleFor(u => u.Name, f => f.Name.FullName()) .RuleFor(u => u.Occupation, f => f.PickRandom(occupations));

var res = faker.Generate(5); Console.WriteLine(string.Join("\n", res));

public class User { public string? Name; public string? Occupation;

public override string ToString()
{
    return $"{Name} {Occupation}";
}

}

The program generates fake user data.

var occupations = new string[] { “gardener”, “teacher”, “writer”, “programmer” }; var faker = new Faker<User>() .RuleFor(u => u.Name, f => f.Name.FullName()) .RuleFor(u => u.Occupation, f => f.PickRandom(occupations));

The fake data is generated using defined rules. With fluent syntax, we generate users with a faker full name and a random occupation, which is picked from the given array.

var res = faker.Generate(5);

We generate five fake users.

public class User { public string? Name; public string? Occupation;

public override string ToString()
{
    return $"{Name} {Occupation}";
}

}

We define the User type with two attributes: Name and Occupation.

$ dotnet run Donny Torphy gardener Ansel Hauck teacher Edyth Friesen programmer Constantin Howe programmer Dayana Gorczany teacher

C# Bogus classic syntax

We can generate fake data with a procedural syntax.

Program.cs

using Bogus;

var faker = new Faker();

var fname = faker.Person.FirstName; var lname = faker.Person.LastName; var email = faker.Person.Email;

Console.WriteLine($"{fname} {lname} {email}");

The program creates a fake data for a person, consisting of a first name, last name, and email.

$ dotnet run Connie Trantow Connie14@hotmail.com

C# Bogus internationalized data

We can create data in various languages.

Program.cs

using Bogus;

var fakerSk = new Faker(“sk”);

var fname = fakerSk.Person.FirstName; var lname = fakerSk.Person.LastName; var email = fakerSk.Person.Email;

Console.WriteLine($"{fname} {lname} {email}");

var fakerRu = new Faker(“ru”);

var fname2 = fakerRu.Person.FirstName; var lname2 = fakerRu.Person.LastName; var email2 = fakerRu.Person.Email;

Console.WriteLine($"{fname2} {lname2} {email2}");

The program creates fake data in Slovak and Russian.

var fakerSk = new Faker(“sk”);

The local is passed to the constructor of the Faker.

$ dotnet run Matej Farkašovský Matej48@gmail.com Валентин Кузьмин Valentin_Kuzmin39@gmail.com

C# Bogus fake data by type

We can generate fake data by type.

Program.cs

using Bogus;

var faker = new Faker<Item>() .RuleForType(typeof(string), f => f.Lorem.Word()) .RuleForType(typeof(int), f => int.MaxValue) .RuleFor(u => u.Weight, f => f.Random.Double(100, 200));

var res = faker.Generate(3); Console.WriteLine(string.Join("\n", res));

public class Item { public string? Name; public int Quantity; public double Weight;

public override string ToString()
{
    return $"{Name} {Quantity} {Weight}";
}

}

In the program, we generate fake data for strings, integers, and doubles.

var faker = new Faker<Item>() .RuleForType(typeof(string), f => f.Lorem.Word()) .RuleForType(typeof(int), f => int.MaxValue) .RuleFor(u => u.Weight, f => f.Random.Double(100, 200));

The rules are based on the types of the attributes of the Item class.

$ dotnet run maxime 2147483647 199.6262336436771 dolore 2147483647 189.21804805485243 tempora 2147483647 111.86314197682654

C# Bogus faking dates

Via the Date property, we can create fake dates.

Program.cs

using Bogus;

var now = DateTime.Now; Console.WriteLine($"{now}");

var faker = new Faker(); Console.WriteLine(faker.Date.Future(20)); Console.WriteLine(faker.Date.Past(50)); Console.WriteLine(faker.Date.Between(new DateTime(2022, 1, 1), new DateTime(2025, 1, 1)));

In the example, we create fake datetime values in the future, past, and between the tiven range.

Console.WriteLine(faker.Date.Future(20));

Here, we create a fake datetime max 20 years in the future.

Console.WriteLine(faker.Date.Past(50));

We create a datetime value max 50 years back in time.

Console.WriteLine(faker.Date.Between(new DateTime(2022, 1, 1), new DateTime(2025, 1, 1)));

This line creates a datetime value between the specified two datetimes.

$ dotnet run 9/8/2022 5:17:07 PM 1/16/2027 6:56:03 PM 1/29/1979 8:21:46 AM 1/12/2023 6:54:39 PM`

Source

Bogus Github page

In this article we have generated fake data in C# using Bogus library.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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