FluentValidation 12.0.0-preview1

Prefix Reserved
.NET 8.0 This package targets .NET 8.0. The package is compatible with this framework or higher.
This is a prerelease version of FluentValidation.
There is a newer version of this package available.
See the version list below for details. 
dotnet add package FluentValidation --version 12.0.0-preview1
                    


                    

                
NuGet\Install-Package FluentValidation -Version 12.0.0-preview1
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package. 
<PackageReference Include="FluentValidation" Version="12.0.0-preview1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
<PackageVersion Include="FluentValidation" Version="12.0.0-preview1" />
                    


                            Directory.Packages.props
                        

                    

                
<PackageReference Include="FluentValidation" />
                    


                            Project file
For projects that support Central Package Management (CPM), copy this XML node into the solution Directory.Packages.props file to version the package. 
paket add FluentValidation --version 12.0.0-preview1
                    


                    

                
#r "nuget: FluentValidation, 12.0.0-preview1"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package. 
#:package FluentValidation@12.0.0-preview1
#:package directive can be used in C# file-based apps starting in .NET 10 preview 4. Copy this into a .cs file before any lines of code to reference the package. 
#addin nuget:?package=FluentValidation&version=12.0.0-preview1&prerelease
                    


                            Install as a Cake Addin
                        

                    

                
#tool nuget:?package=FluentValidation&version=12.0.0-preview1&prerelease
                    


                            Install as a Cake Tool

FluentValidation is validation library for .NET that uses a fluent interface and lambda expressions for building strongly-typed validation rules.

Supporting the project

If you use FluentValidation in a commercial project, please sponsor the project financially. FluentValidation is developed and supported by @JeremySkinner for free in his spare time and financial sponsorship helps keep the project going. You can sponsor the project via either GitHub sponsors or OpenCollective.

Example

With FluentValidation, you can define a class that inherits from AbstractValidator which contains the rules for a particular class. The example below shows how you could define rules for a Customer class, and then how to execute the validator.

using FluentValidation;

public class CustomerValidator: AbstractValidator<Customer> {
  public CustomerValidator() {
    RuleFor(x => x.Surname).NotEmpty();
    RuleFor(x => x.Forename).NotEmpty().WithMessage("Please specify a first name");
    RuleFor(x => x.Discount).NotEqual(0).When(x => x.HasDiscount);
    RuleFor(x => x.Address).Length(20, 250);
    RuleFor(x => x.Postcode).Must(BeAValidPostcode).WithMessage("Please specify a valid postcode");
  }

  private bool BeAValidPostcode(string postcode) {
    // custom postcode validating logic goes here
  }
}

var customer = new Customer();
var validator = new CustomerValidator();

// Execute the validator.
ValidationResult results = validator.Validate(customer);

// Inspect any validation failures.
bool success = results.IsValid;
List<ValidationFailure> failures = results.Errors;

Full Documentation

Full documentation can be found at https://docs.fluentvalidation.net

Release Notes and Change Log

Release notes can be found on GitHub.

Product Compatible and additional computed target framework versions.
.NET net8.0 is compatible.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed.  net9.0 was computed.  net9.0-android was computed.  net9.0-browser was computed.  net9.0-ios was computed.  net9.0-maccatalyst was computed.  net9.0-macos was computed.  net9.0-tvos was computed.  net9.0-windows was computed.  net10.0 was computed.  net10.0-android was computed.  net10.0-browser was computed.  net10.0-ios was computed.  net10.0-maccatalyst was computed.  net10.0-macos was computed.  net10.0-tvos was computed.  net10.0-windows was computed. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

  • net8.0

    • No dependencies.

NuGet packages (2.9K)

Showing the top 5 NuGet packages that depend on FluentValidation:

Package Downloads
FluentValidation.DependencyInjectionExtensions

Dependency injection extensions for FluentValidation
FluentValidation.AspNetCore

AspNetCore integration for FluentValidation
Ocelot

Ocelot is an API gateway based on .NET stack.
Reo.Core.DataModels

Package Description
Reo.Core.Validation

Package Description

GitHub repositories (254)

Showing the top 20 popular GitHub repositories that depend on FluentValidation:

Repository Stars
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Full Modular Monolith application with Domain-Driven Design approach.
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ASP.NET Boilerplate - Web Application Framework
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Sample ASP.NET Core 8.0 reference application, now community supported: https://github.com/NimblePros/eShopOnWeb
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Blazor Component Library based on Material Design principles with an emphasis on ease of use and extensibility
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Web Application ASP.NET 9 using Clean Architecture, DDD, CQRS, Event Sourcing and a lot of good practices
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A light-weight REST API development framework for ASP.NET 8 and newer.
Prowlarr/Prowlarr
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jasontaylordev/NorthwindTraders
Northwind Traders is a sample application built using ASP.NET Core and Entity Framework Core.
Lidarr/Lidarr
Looks and smells like Sonarr but made for music.
microsoft/RulesEngine
A fast and reliable .NET Rules Engine with extensive Dynamic expression support
fullstackhero/blazor-starter-kit
Clean Architecture Template for Blazor WebAssembly Built with MudBlazor Components.
Megabit/Blazorise
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Version Downloads Last Updated
12.1.0 571,374 11/3/2025
12.0.0 18,418,996 5/5/2025
12.0.0-preview1 250,686 1/2/2025
11.12.0 51,331 11/3/2025
11.11.0 47,691,763 11/16/2024
11.10.0 20,869,481 9/15/2024
11.9.2 27,648,810 6/10/2024
11.9.1 14,156,868 4/23/2024
11.9.0 34,292,592 12/21/2023
11.8.1 9,906,005 11/22/2023
11.8.0 10,034,642 10/19/2023
11.7.1 12,185,937 8/12/2023
11.7.0 143,732 8/11/2023
11.6.0 9,286,369 7/4/2023
11.5.2 20,416,590 4/7/2023
11.5.1 68,399,776 2/20/2023
11.5.0 3,207,337 2/13/2023
11.4.0 20,287,049 11/23/2022
11.3.0 3,795,806 11/10/2022
11.2.2 17,285,191 9/11/2022
11.2.1 24,083,158 8/28/2022
11.2.0 7,902,988 8/8/2022
11.1.1 684,718 8/6/2022
11.1.0 13,714,040 6/22/2022
11.0.3 3,726,514 6/10/2022
11.0.2 5,678,078 5/27/2022
11.0.1 6,991,415 5/7/2022
11.0.0 7,059,557 4/30/2022
10.4.0 21,670,454 3/11/2022
10.3.6 28,154,780 12/13/2021
10.3.5 3,312,944 11/30/2021
10.3.4 10,605,581 10/22/2021
10.3.3 12,526,504 8/24/2021
10.3.1 755,226 8/19/2021
10.3.0 8,754,305 7/9/2021
10.2.3 8,769,887 6/3/2021
10.2.2 477,646 6/1/2021
10.2.1 1,396,479 5/30/2021
10.2.0 395,291 5/28/2021
10.1.0 5,646,210 4/28/2021
10.0.4 4,394,323 4/17/2021
9.5.4 7,649,112 4/5/2021
9.5.3 4,148,349 3/15/2021
9.5.2 2,069,548 3/8/2021
9.5.1 6,928,352 2/11/2021
9.5.0 3,499,316 1/31/2021
9.4.0 3,170,776 1/14/2021
9.3.0 15,282,964 11/10/2020
9.3.0-preview3 40,090 10/19/2020
9.3.0-preview2 154,492 9/15/2020
9.3.0-preview1 13,695 8/26/2020
9.2.2 7,314,929 9/20/2020
9.2.1 33,676 9/19/2020
9.2.0 8,131,492 8/26/2020
9.1.3 1,047,714 8/19/2020
9.1.2 992,047 8/12/2020
9.1.1 687,691 8/8/2020
9.1.0 320,281 8/8/2020
9.0.1 5,699,308 7/14/2020
9.0.0-preview5 90,651 5/23/2020
9.0.0-preview4 147,536 4/22/2020
9.0.0-preview3 208,780 2/29/2020
9.0.0-preview2 32,725 2/21/2020
9.0.0-preview1 101,356 2/8/2020
8.6.3 7,986,090 8/28/2020
8.6.2 29,551,409 2/29/2020
8.6.1 13,343,680 12/28/2019
8.6.0 4,417,152 12/4/2019
8.5.1 3,957,543 11/2/2019
8.5.0 6,753,730 9/24/2019
8.5.0-preview5 70,912 9/1/2019
8.5.0-preview4 103,186 7/23/2019
8.5.0-preview3 32,796 7/10/2019
8.5.0-preview2 89,601 6/13/2019
8.5.0-preview1 64,634 5/10/2019
8.4.0 15,108,358 5/10/2019
8.3.0 4,219,971 4/24/2019
8.2.3 743,580 4/12/2019
8.2.2 1,147,734 4/5/2019
8.2.1 506,658 4/4/2019
8.2.0 1,110,031 3/26/2019
8.1.3 5,248,137 1/25/2019
8.1.2 2,414,270 12/18/2018
8.1.1 621,792 12/11/2018
8.1.0 853,864 12/6/2018
8.1.0-preview2 29,930 11/14/2018
8.1.0-preview1 28,235 10/14/2018
8.0.101 964,160 11/24/2018
8.0.100 4,173,278 9/4/2018
8.0.0 1,181,841 8/16/2018
8.0.0-rc1 54,581 7/24/2018
8.0.0-preview4 26,137 7/16/2018
8.0.0-preview3 24,742 7/13/2018
8.0.0-preview2 24,594 7/13/2018
7.6.105 1,897,395 8/11/2018
7.6.104 2,838,363 7/6/2018
7.6.103 1,331,873 6/16/2018
7.6.102 344,957 6/14/2018
7.6.101 78,139 6/13/2018
7.6.100 181,666 6/7/2018
7.6.0 412,608 6/1/2018
7.6.0-preview1 53,145 4/12/2018
7.5.2 4,013,718 3/16/2018
7.5.1 283,561 3/11/2018
7.5.0 757,121 2/26/2018
7.4.0 2,400,226 1/26/2018
7.3.4 1,144,841 1/2/2018
7.3.3 199,997 12/22/2017
7.3.2 76,999 12/21/2017
7.3.1 350,721 12/13/2017
7.3.0 128,591 12/13/2017
7.3.0-beta3 28,613 12/8/2017
7.3.0-beta2 47,701 11/20/2017
7.3.0-beta1 25,439 11/11/2017
7.2.1 2,974,685 10/24/2017
7.2.0 853,940 10/5/2017
7.2.0-beta3 41,887 9/5/2017
7.2.0-beta2 27,703 8/22/2017
7.2.0-beta1 23,909 8/19/2017
7.1.1 2,428,273 7/25/2017
7.1.0 565,564 6/28/2017
7.1.0-beta1 23,685 6/24/2017
7.0.3 766,235 6/7/2017
7.0.2 292,650 5/26/2017
7.0.1 99,487 5/23/2017
7.0.0 760,982 5/19/2017
7.0.0-beta3 74,713 5/1/2017
7.0.0-beta2 27,363 4/17/2017
7.0.0-beta1 24,956 4/7/2017
6.4.1 2,253,866 3/15/2017
6.4.1-beta1 23,973 3/13/2017
6.4.0 1,079,877 3/3/2017
6.4.0-rc4 146,751 2/13/2017
6.4.0-rc3 39,925 2/3/2017
6.4.0-rc2 39,985 1/30/2017
6.4.0-rc1 23,779 1/30/2017
6.4.0-beta9 91,813 11/21/2016
6.4.0-beta8 50,784 10/31/2016
6.4.0-beta7 24,435 10/28/2016
6.4.0-beta6 24,724 10/25/2016
6.4.0-beta5 24,298 10/24/2016
6.4.0-beta4 24,403 10/21/2016
6.4.0-beta3 71,778 7/4/2016
6.4.0-beta2 25,295 7/1/2016
6.4.0-beta10 23,494 1/30/2017
6.4.0-beta1 28,693 6/28/2016
6.3.4-alpha 436,079 6/1/2016
6.3.3-alpha 23,289 5/27/2016
6.2.1 5,565,838 2/26/2016
6.2.1-beta1 28,769 2/24/2016
6.2.0 172,725 2/22/2016
6.2.0-beta1 24,619 2/12/2016
6.1.0 442,057 1/18/2016
6.0.2 118,413 1/5/2016
6.0.1 40,242 1/5/2016
6.0.0 136,251 12/22/2015
5.6.2 1,644,181 5/29/2015
5.6.1 35,055 5/29/2015
5.5.0 1,230,665 10/31/2014
5.4.0 614,607 7/3/2014
5.3.0 106,006 5/27/2014
5.2.0 77,276 5/21/2014
5.1.0 1,077,618 3/11/2014
5.0.0.1 566,552 10/24/2013
4.0.0.1 309,170 7/18/2013
4.0.0 121,480 4/29/2013
3.4.6 432,530 8/30/2012
3.4.0 72,516 8/17/2012
3.3.1 94,159 3/30/2012
3.2.0 78,877 11/14/2011
3.1.0 53,296 7/30/2011
3.0.0.1 26,558 7/5/2011
3.0.0 47,605 6/25/2011
2.0.0 78,112 1/9/2011
1.3.0 445,698 1/7/2011

FluentValidation 12 is a major release. Please read the upgrade guide at https://docs.fluentvalidation.net/en/latest/upgrading-to-12.html

Full release notes can be found at https://github.com/FluentValidation/FluentValidation/releases