Koto.Validation 0.3.0-preview.3

.NET 10.0 This package targets .NET 10.0. The package is compatible with this framework or higher.
This is a prerelease version of Koto.Validation. 
dotnet add package Koto.Validation --version 0.3.0-preview.3
                    


                    

                
NuGet\Install-Package Koto.Validation -Version 0.3.0-preview.3
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="Koto.Validation" Version="0.3.0-preview.3" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
<PackageVersion Include="Koto.Validation" Version="0.3.0-preview.3" />
                    


                            Directory.Packages.props
                        

                    

                
<PackageReference Include="Koto.Validation" />
                    


                            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 Koto.Validation --version 0.3.0-preview.3
                    


                    

                
#r "nuget: Koto.Validation, 0.3.0-preview.3"
#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 Koto.Validation@0.3.0-preview.3
#: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=Koto.Validation&version=0.3.0-preview.3&prerelease
                    


                            Install as a Cake Addin
                        

                    

                
#tool nuget:?package=Koto.Validation&version=0.3.0-preview.3&prerelease
                    


                            Install as a Cake Tool

Koto.Validation

FluentValidation extensions and a CQRS pipeline behavior for the Koto suite.

Uses FluentValidation v12 (Apache 2.0 on all versions), pinned to [12.0.0,13.0.0).

Install

dotnet add package Koto.Validation

What's included

Type Purpose
KotoValidators.MustBeValueObject<T, TSource, TValueObject> Validates a property by calling a domain factory (Func<TSource, Result<TVO>>) — any source type: string, int, Guid, …
KotoValidators.MustBeEntity<T, TElement, TEntity> Same contract for entity factories (reads naturally for entities)
KotoValidators.ListMustContainNumberOfItems Min/max count rule for collections
KotoValidators.NotEmptyWithKotoError / LengthWithKotoError Built-in rules carrying Errors.General codes
ValidationBehavior<TRequest, TResponse> Pipeline middleware — runs all validators (async-capable) before the handler
ServiceCollectionExtensions.AddKotoValidation Registers the behavior and scans assemblies for validators

Usage

Register

builder.Services.AddKotoValidation(typeof(Program).Assembly);
// Registers ValidationBehavior<,> as an open generic and scans for IValidator<T> —
// no extra registration needed. Recommended behavior order: Logging → Validation → Transaction.

Write a validator — one source of truth

The validation logic lives in the domain factory; the validator only calls it:

public sealed class PlaceOrderValidator : AbstractValidator<PlaceOrderCommand>
{
    public PlaceOrderValidator()
    {
        RuleFor(x => x.Email).MustBeValueObject(Email.Create);      // string source
        RuleFor(x => x.Quantity).MustBeValueObject(Quantity.Create); // int source — any type works
        RuleFor(x => x.Items).ListMustContainNumberOfItems(1, 100);
        RuleFor(x => x.CustomerId).NotEmpty();
    }
}

Validators are keyed by the concrete command type and discovered by the pipeline automatically (the dispatcher closes ValidationBehavior<,> over PlaceOrderCommand).

Structured errors

Each domain Error travels as structured state — ValidationFailure.CustomState + ErrorCode — not as a serialized message string. On failure, ValidationBehavior returns a Result carrying one Error per validation failure, each with its real Code, Message, and Field (the property name). Nothing is collapsed into a single string; HTTP layers can render RFC 7807 validation problem details per field (see Koto.Api.AspNetCore).

Async rules (MustAsync, CustomAsync) are fully supported — the behavior calls ValidateAsync.

Product Compatible and additional computed target framework versions.
.NET net10.0 is compatible.  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.

NuGet packages

This package is not used by any NuGet packages.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last Updated
0.3.0-preview.3 48 7/11/2026
0.3.0-preview.2 49 7/11/2026
0.3.0-preview.1 50 7/3/2026
0.2.0-preview.1 59 6/28/2026
0.1.0-preview.5 70 5/13/2026
0.1.0-preview.4 58 5/13/2026
0.1.0-preview.3 58 5/13/2026
0.1.0-preview.2 63 5/11/2026