Fluentvalidation multiple properties SetValidator(New MyCustomerDiscountValidator); If you need to specify the same condition for multiple rules then you can call the top-level When method instead of chaining the When call at the end of the rule: Feb 24, 2025 · Is there a way to return multiple messages on one rule? public class EmployeeValidator : AbstractValidator<Employee> { public EmployeeValidator () { RuleFor (p => p. You can either define multiple rules for each of the interface implementors, or you can use a custom property validator to do runtime inspection on the type. How Cross-Field Validation Works in FluentValidation In FluentValidation, cross-field validation can be implemented by accessing multiple properties within a single validator. Now let’s create the methods responsible for implementing Product entity validation. Is there a way to implement a validation globally for all string properties using FluentValidator. Anon Anon 2 Answers You can take advantage of the Must overload that gives you access to the whole class object so that you can do a property validation against other properties. Let’s use some constants to easily identify and maintain the different validation rules in the application. I'll rather focus on extending the library with your own custom validation. I've just come across a similar problem and the latest version of FluentAssertions has changed things a bit. A. Nov 10, 2016 · Is it possible to have multiple messages defined seperatly for one rule? Currently only the last "WithMessage" is shown and I assume the previous ones are overwritten. Jan 6, 2016 · I started by creating AbstractValidator<T> derived validation classes for each class in my object model to validate their properties. it's the job of the individual property validators to decide how many ValidationErrors they create, rather than the rule definition doing this. i am using a method to validate value from database which return's integer value -1, -2 and -3 for different error Apr 28, 2022 · FluentValidation, validate a property based on another properties value Asked 3 years, 6 months ago Modified 3 years, 6 months ago Viewed 3k times Oct 24, 2023 · A while ago, I wrote about using fluent assertions. This allows you to split rules across multiple classes and compose them together (in a similar way to how other languages support traits). The scenario I have is around testing Json serialization where I ignore certain properties. To inject a validator for a specific model, you should register the validator with the service provider as IValidator<T>, where T is the type of object being validated. Blazor ¶ FluentValidation does not provide integration with Blazor out of the box, but there are several third party libraries you can use to do this: To add a validation rule to the target property, simply call the relevant method on the rule chain builder (passing in any parameters as necessary). Let me introduce you to FluentValidation, which follows the same concept as fluent assertions but for validations and rules. Dec 21, 2023 · Explore the differences between Fluent Validation and traditional validation in . Read our blog9/18/17 Creating Complex Validation Rules Using Fluent Validation with ASP. Nov 8, 2016 · How to exclude multiple properties in FluentAssertions ShouldBeEquivalentTo () Asked 9 years ago Modified 3 years, 10 months ago Viewed 17k times Jun 15, 2025 · Introduction Learn how to use rule sets which allow developers to group validation rules together which can be executed together as a group whilst ignoring other rules or execute all rules. May 31, 2021 · I am trying to write validation rule for multiple string properties, to check whether they are unique. FluentValidation 12 supports . ClassLevelCascadeMode, and their global defaults were introduced in FluentValidation 11 In older versions, there was only one property controlling cascade modes: AbstractValidator. InstanceToValidate property (although you'd need to cast it to the right type) Also if you use the Must method rather than Custom, you can always retrieve the root instance as a typed parameter (see https://docs. Oct 3, 2018 · Thanks Hassan for the input but I am looking to achieve the same rule applying for multiple properties. It shows usage of example of When and Unless methods. No response Describe the solution you'd like I would like to enrich the validation message on complex properties of the same type. When I use the first part of the code bellows, it works as expected; but when I use the second part, only the first validation is executed, ignoring the last two validation rules. FluentValidation is a popular library in C# for writing validation rules. My objects contains dictionaries of other objects. In ASP. 0 Issue Description When trying to test a Nullable property (e. Aug 28, 2022 · I want to validate model with same method (CustomerFound) for multiple properties in my model (first I want to check combination of CustomerId + CarID and secondly CustomerPartnerId + CarId). For example, this rule on the CustomerDiscount property will only execute when IsPreferredCustomer is true: Oct 10, 2011 · FluentValidation - validating across multiple properties Asked 14 years ago Modified 14 years ago Viewed 25k times Nov 7, 2017 · I have a business rule that says that PropertyA should be a multiple of PropertyB. If you need to specify the same condition for multiple rules then you can call the top-level When method instead of chaining the When call at the end of the rule: Mar 15, 2024 · The biggest problem with FluentValidation Spoiler: it allows invalid objects to exist In this article, I’ll review commonly brought-up benefits of FluentValidation and present arguments against … Oct 14, 2020 · This includes customizing the index name, creating unique indexes, and creating multi-column indexes. ASP. Jan 2, 2025 · FluentValidation is a popular . FluentVali May 6, 2024 · Learn how to make powerful validations in your ASP. CascadeMode. FluentValidation ¶ FluentValidation is a . ---This video is based on the questio Feb 21, 2024 · FluentValidation version 11. 4. itemB). RuleLevelCascadeMode, AbstractValidator. If your validator contains rules for several properties you can limit execution to only validate specific properties by using the IncludeProperties option: In the above example only the rule for the Surname property will be executed. Test Extensions ¶ FluentValidation provides some extensions that can aid with testing your validator classes. Feb 18, 2021 · How do I validate multiple properties with the same rule, without showing multiple errors? #1644 Closed MrYossu opened on Feb 18, 2021 Dependent Rules ¶ By default, all rules in FluentValidation are separate and cannot influence one another. Here's an example: Introduction Edit this page Getting started Fluent Assertions is a set of . The fluent API makes validators easy to write and understand. Apr 29, 2024 · Cross-property validation ensures that related properties are validated together, group validation allows conditional validation based on multiple properties, and asynchronous validation enables validation logic that requires asynchronous operations. NET Core May 21, 2025 · Validating Inputs with FluentValidation Learn how to implement robust input validation in Clean Architecture using FluentValidation. NET Core Web API Applications. You can always access the root instance from the context. In this FluentValidation in C# tutorial, I will show you how easy it is to validate objects. . If you need support for older runtimes, use FluentValidation 11 which runs on . NET library for building strongly-typed validation rules. NET version No response Summary When I define multiple custom validators for the same model and property and there are validation errors occurring in more than one validators, some validation results a FluentValidation rule for multiple propertiesI have a FluentValidator that has multiple properties like zip and county etc. Nov 8, 2010 · I really like Jeremy Skinner’s FluentValidation library and have used it on a couple of projects. The Jul 21, 2017 · It's very common that we assert if two objects are equivalent in unit tests. Property validators are the fundamental building blocks that perform actual validation logic on individual properties. The objects in the dictionaries contain other objects that I want to exclude. This might be because the value of the property cannot be predicted or you just don't want to include Oct 22, 2021 · I have 2 classes in model and I would like to validate that value in a field from one class is smaller than field from second class. I've looked and looked but I haven't been able to find any solution so sorry in advance if I have Including Rules ¶ You can include rules from other validators provided they validate the same type. The error message for each validator can contain special placeholders that will be filled in when the error message is constructed. Mar 11, 2024 · When to Use Validate properties of a class, such as DTOs (Data Transfer Objects) or domain models. For example, imagine you have the following validator defined in your project: Inheritance Validation ¶ As of FluentValidation 9. For these examples, we’ll imagine a scenario where you want to create a reusable validator that will ensure a List object Conditions ¶ The When and Unless methods can be used to specify conditions that control when the rule should execute. To define a validation rule that involves multiple properties, you can use the Custom method to write a custom validation rule that accesses multiple properties. total). Which will: Enforce that all properties are evaluated. And sometimes there are properties that are interdependent on each other, but appear in multiple models. Dec 16, 2021 · I'm tring to build a validation rule using FluentValidation lib. ShouldBeEquivalentTo(expected); However, there are times where you want to exclude certain properties when comparing objects. NET MVC's client-side validation, but not all rules are supported. Apr 6, 2022 · Is your feature request related to a problem? Please describe. Packed with actionable tips, tricks, and best practices, learn how to seamlessly integrate sophisticated validation logics into your applications for improved performance and reliability. The conventional use of Fluent Validation is to create a model followed by creating a validator class. , matching passwords, date ranges), FluentValidation provides a straightforward way The Unless method is simply the opposite of When. The `CascadeMode` property was deprecated in FluentValidation 11 and removed in FluentValidation 12. NET and has extensive integration points, making it suitable for various types of In C#, FluentValidation is a popular library for creating complex validation rules. NET Core 3. NET Core Web API, validation can be implemented in multiple ways, including: Data Annotations: This involves decorating model properties with attributes such as [Required], [StringLength], etc. AttributeSet> { private string Keyvalue = string. g. NET Core Web API Applications with Examples. Using FluentAssertion, this looks like the following actual. Nov 2, 2012 · Please specify either a custom property name by calling 'WithName'. We could group the Surname and Forename rules together in a “Names” RuleSet: Sep 13, 2016 · There isn't really a good way to do that at the moment. NET Standard 2. _service method returns list Aug 26, 2021 · I can't seem to find a way to validate multiple properties together. For example, imagine the following example: Nov 24, 2022 · This article is about conditional validation using Fluent Validation. CustomerDiscount) . For I am trying out FluentValidation on a project that contains complex view models and I read the documentation here but I don't see how to set up the rules to validate a list of objects declared in my view model. DependencyInjection. Validating multiple properties in C# is crucial for ensuring the correctness and consistency of your data. May 5, 2025 · Compare Data Annotations and Fluent Validation in . The article is a short introduction. NET 5 and newer. 1, . It supports . e. NET. NET along with working code samples to validate library object. I quickly realized that I was duplicating code to validate the Name properties of the various classes, so decided to create a NameValidator custom property validator (i. This technique allows for more fluent, understandable, and expressive assertion writing. Jan 16, 2023 · Validations A “RuleSet” is a way to group multiple validation rules together in FluentValidation. For example, any rules defined using a condition (with When/Unless), custom validators, or calls to Must will not run on the client side. NET Core web applications to validate incoming models. Oct 10, 2016 · public class AValidator : AbstractValidator<A> { public AValidator() { RuleFor(x => x. Usually the solution is to review the models and put these properties in their own model, which would have it's own validator to call. You could technically do this with a custom validator that does the work, but I wouldn't really recommend it. NET 8 and newer. It was developed to provide a more flexible and customizable alternative to the Data Annotations. It has four properties: Color, Make, Model, Year. As you see, the validation isn't taking care of a property alone, but needs to validate 2 interrelated properties. NET library that simplifies validation logic by providing an expressive and fluent interface for defining rules. WithMessage("Please ensure you have selected the A object"); } } But during client-side validation for A. Let's say I have a Car class. NET Core Web API with Real-time Examples. This enables a simple intuitive syntax that all starts with the following using statement: May 2, 2020 · FluentValidation: Using a parent property value in a child collection rule Asked 5 years, 6 months ago Modified 3 years, 1 month ago Viewed 9k times FluentValidation is a popular library in C# for writing validation rules. The `RuleLevelCascadeMode` and `ClassLevelCascadeMode` properties should be used instead. DateTime?) that has some validation rules and then using ShouldHaveValidationErrorFor` it doesn't throw an error, when it Dec 10, 2016 · How to organize FluentValidation rules so that they may be reused in multiple validators? Asked 8 years, 11 months ago Modified 4 years ago Viewed 11k times Complex Business Rules: If your validation logic involves multiple properties of the model or complex business rules that depend on external data, Fluent API Custom Validators allow you to encapsulate this logic neatly. dev Nov 16, 2018 at 17:16 Creating your first validator ¶ To define a set of validation rules for a particular object, you will need to create a class that inherits from AbstractValidator <T>, where T is the type of class that you wish to validate. I went through Fluent documentation but I cannot find a real exa May 24, 2022 · So the goal is to be able to evaluate all properties in one go. It is attribute-based validation directly on model properties. We recommend treating validators as ‘black boxes’ - provide input to them and then assert whether the validation results are correct or incorrect. Rulesets preferable for case of question, but this ability is more "low-level" and must have attention of FluentValidation community. This is similar to this answer. Jan 26, 2022 · With FluentValidation, we can check if properties are empty or null, and also if numeric fields are greater than zero. Up until now though, I’ve only be using it to validate single properties in isolation. The library allows you to build validation rules using a fluent interface, which leads to cleaner and more readable code. My problem is that I'd like to select different validators for the the complete object given a specific properties of the Custom Error Codes ¶ A custom error code can also be associated with validation rules by calling the WithErrorCode method: Nov 1, 2024 · Multi-Field Validation: When you need to validate multiple properties of a model in relation to each other (e. itemA + p. NET framework used to validate objects and values of properties inside an object. It also provides an easy way to create validation rules for the properties in your models/classes, taking out the complexity of validation. RuleSets allow you to group validation rules together which can be executed together as a group whilst ignoring other rules: For example, let’s imagine we have 3 properties on a Person object (Id, Surname and Forename) and have a validation rule for each. 2, if your object contains a property which is a base class or interface, you can set up specific child validators for individual subclasses/implementors. Property name resolution is also pluggable. net Sep 9, 2024 · Cool answer, didn't know about ability of multiple validators being registered and resolved. Feb 25, 2025 · FluentValidation is a popular . EigenSchema. 9. RuleFor(foo=> f Nov 9, 2012 · I am trying to implement a complex validation scenario in FluentValidation. The recommended way is to make use of the Predicate Validator to write a custom validation function, but you can also use the Custom method to take full control of the validation process. When it comes to Validating Models and incoming HTTP Requests, aren't we all leaning toward Data Annotations? Although it can be quick to set up Data Annotations on your models, there are a few drawbacks to this approach. Oct 3, 2023 · Dyamic Validation using FluentValidation Validation in a C# class is an area where configuration / customization pressures can sneak into an application. It occurred to me that the code I was specializing was ignoring the value property, and both an overload for that and an overload that creates a default instance would make sense. Mar 15, 2022 · 2 Is there a way to validate for null more than one properties in a fluent manner? For example, without using Fluentvalidator, this may be possible by implementing IValidatableObject. ruleFor. This guide demonstrates how to create custom validation rules, integrate validators with dependency injection, and ensure data integrity across your application layers. Here you can find validators, that are supported on the client-side: NotNull/NotEmpty Matches (regex) InclusiveBetween (range) CreditCard Email EqualTo (cross-property equality comparison) Length Other Advanced Features ¶ These features are not normally used in day-to-day use, but provide some additional extensibility points that may be useful in some circumstances. The result of such a call is again the rule chain builder, so you can specify multiple rules in a single call to . For example, imagine you have 2 validators that validate different aspects of a Person: Creating your first validator ¶ To define a set of validation rules for a particular object, you will need to create a class that inherits from AbstractValidator<T>, where T is the type of class that you wish to validate. I want to In this article, I will discuss How to Implement Fluent API Conditional Validations in ASP. Extensions. This means you can define validation logic in a more readable and maintainable way compared to using Data… Dec 19, 2015 · RuleFor(customer => customer. You can find a lot of information about basic usage and even more advanced scenarios in very detailed documentation. Implement complex validation rules involving multiple properties or conditions. Dec 19, 2017 · Multiple Dependent Rules FluentValidation Asked 7 years, 11 months ago Modified 4 years, 8 months ago Viewed 14k times Learn how to create custom validation logic with Fluent API custom validators in ASP. I want to construct a validation rule Sep 2, 2019 · System Details FluentValidation version: 8. At FluentValidation rule for multiple properties , @Matías Romero suggests using something like May 19, 2014 · FluentValidation is a small portable validation library with fluent interface. The problem is I have very little experience with expressions and delegates in C#. NET development with this expert guide to using FluentValidation. Dec 11, 2019 · FluentValidation is a . How can I change it to my string from the validator? FluentValidation ¶ FluentValidation is a . NotEmpty() . NET and ASP. You can use DependentRules to do this. This enables a simple intuitive syntax that all starts with the following using statement: Apr 1, 2015 · I'm attempting to validate that only one of three fields has a value using FluentValidation. Is there any way to implement this or am I trying to use FluentValidation in a way that it's not meant to be used? May 11, 2020 · Hi. GreaterThan(0) . Discover a clear, organized approach to validate for `null` values in multiple properties using FluentValidation in C# . NET Core ¶ FluentValidation can be used within ASP. 0 ASP. for example First Name, Last Name and Gender needs to be validated for the Is Not Null and I Dependency Injection ¶ Validators can be used with any dependency injection library, such as Microsoft. To use dependent rules, call the DependentRules method at In the above example only the rule for the Surname property will be executed. Nov 27, 2015 · I have a class containing one string property: public class Bla { public string Parameter { get; set; } } I would like to write a custom AbstractValidator, which checks that Parameter is equal May 4, 2020 · Ah, yes you're correct - e in that case would be the value of the property, rather than the root instance. However, there may be some cases where you want to ensure that some rules are only executed after another has completed. Mar 24, 2021 · You can take advantage of the Must overload that gives you access to the whole class object so that you can do a property validation against other properties. Apr 14, 2016 · i am validating input values with FluentValidation. However, #912 made me realize there may need to be a more generic way to set multiple properties. FluentValidation ships with several built-in validators. When working with sub-properties of collections, you can use a wildcard indexer ([]) to indicate all items of a collection. The “RuleSet” method can be used to specify the name of the RuleSet and a lambda function that contains the validation rules for that RuleSet. The other day a colleague and I were trying to create a rule that validated two properties by querying the database and checking that… Custom Validators ¶ There are several ways to create a custom, reusable validator. By default, the name of the property extracted from the MemberExpression passed to RuleFor. These properties can both be null. NET Core applications using FluentValidation. NET version No response Summary When I define multiple custom validators for the same model and property and there are validation errors occurring in more than one validators, some validation results a Dec 15, 2015 · I'm using FluentValidation (C#) to achieve validation of a complex object. You can specify multiple index annotations on a single property by passing an array of IndexAttribute to the constructor of IndexAnnotation. See FluentValidation rule for multiple properties for more details. Big +1! May 25, 2025 · This document covers the core property validation infrastructure in FluentValidation, including the IPropertyValidator interface, PropertyValidator base class, and the various specialized validator implementations. This is intentional and necessary for asynchronous validation to work. Aug 8, 2024 · By creating a validator class and defining rules using FluentValidation, you can validate multiple properties in a structured and maintainable way. Learn to create custom validation methods for stream Sep 28, 2018 · I've updated the extensions above to add two more overloads. In this article, I will discuss How to Validate Nested Complex or Collection Property using Fluent API in ASP. Learn key differences, pros, and best use cases. Empty; public MandatoryValidator(string keyvalue) Jan 7, 2023 · FluentValidation tips FluentValidation is a popular . Id) . A simplistic solution that checks if a user ID is already in use using an external web As for your second question, FluentValidation works with client-side validation, but not all rules are supported. You can use this library to replace Data Annotations in your web application or applications that do not natively support Data Annotations. They both have separate validation rules but they cannot both have a value set. 0, . IE validatorP. May 19, 2022 · my code : public class MandatoryValidator : AbstractValidator<Entity. WithMessa Aug 10, 2023 · Is your feature request related to a problem? Please describe. For example, imagine that you have a Customer class: Sep 5, 2018 · 19 Ok, got an answer from FluentValidation's github-issues: Hi, this is related to you use of the When condition. NET library for building strongly-typed validation rules in a fluent interface. For example, imagine that you have a Customer class: Mar 31, 2020 · 5 I want to validate two properties (MyProperty1, MyProperty2) in a class. Option 1: Multiple rule definitions with a type filter With this option, you create a specific rule definition for each potential implementor of the interface: Sep 23, 2019 · Here was the response from JeremySkinner: Hi, FluentValidation only performs validation on a pre-populated object, it doesn't modify/change the values of properties. I'll have a think about how best to add an extensibility point that could be used to support this. Apr 28, 2024 · In this article we are going to learn more about different Validators with FluentValidation, that we can use to protect our app from bad inputs. so i made validator to check it. NET Core for cleaner, flexible model validation. By default, a When condition applies to all previous validators in the same RuleFor call, so when you use a single call to RuleFor, you’re essentially doubling up on conditions. Note that FluentValidation will also work with ASP. Dec 3, 2021 · I want to validate all string properties globally, so that they do not start with "=" character. This guide will take you through the key aspects of Apr 9, 2025 · Discover how to efficiently validate multiple properties in your model using `Fluent Validation` in C# . It allows you to write different rules without much effort thanks to its out of the box rule sets validators. There are several approaches for doing this: Manual validation Automatic validation (using the ASP. If you want to change this logic, you can set the DisplayNameResolver property on the ValidatorOptions class: Asynchronous Validation ¶ In some situations, you may wish to define asynchronous rules, for example when working with an external API. Aug 14, 2020 · There's a couple of different ways to do this. NET extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style unit test. Allow us to get a summary of all failing properties in one test run (rather than having to fix one property, run the test and then see where the next one fails etc) Something along the lines of: Jun 9, 2015 · C# FluentValidation for a hierarchy of classes Asked 10 years, 5 months ago Modified 5 years, 8 months ago Viewed 37k times Apr 4, 2021 · How can I use 4 conditions in RuleFor () along with single ErrorCode () and WithMessage () FluentValidation rule for multiple propertiesI have a FluentValidator that has multiple properties like zip and county etc. Changing this value would set the cascade mode at both validator class-level and rule-level. May 2, 2020 · FluentValidation: Using a parent property value in a child collection rule Asked 5 years, 6 months ago Modified 3 years, 1 month ago Viewed 9k times FluentValidation is a popular library in C# for writing validation rules. Nov 16, 2018 · Possible duplicate of FluentValidation multiple validators – Wim Ombelets Nov 16, 2018 at 13:21 @WimOmbelets I saw this post, in my case I am trying to call different validations for FOO and not different validations of different properties of FOO – alex. This is done through the Must() method, which allows you to define complex custom logic that can reference multiple properties on the same object. Here's an example: Feb 22, 2017 · I want to group these properties in one rule that validate each property through these validation rules (NotEmpty, Length) How to do this in fluent validation ? I am using FluentValidation and I want to format a message with some of the object's properties value. Id I still have a default validation message: 'Id' must not be empty. In the example below, each property has there own validator class which allows reuse. Fluent Validation: Writing validation rules in a separate class with a fluent Jun 30, 2023 · FluentValidation is an open-source validation library for . Equal(p. By default, FluentValidation allows custom rules defined with MustAsync or CustomAsync to be run asynchronously, as well as defining asynchronous conditions with WhenAsync. StartDate). I've recently started using Fluent Validation for one of my projects and have run into a issue. fluentvalidation. Say I have a property that must be validated against other properties like so RuleFor(i => i. NET validation pipeline) Automatic validation (using a filter) With manual validation, you inject the validator into your controller (or api endpoint), invoke the validator and act upon The AbstractValidator. custom PropertyValidator derived class). Jul 5, 2023 · C# FluentValidation tutorial shows how to validate data in C# using FluentValidation library. Blazor ¶ FluentValidation does not provide integration with Blazor out of the box, but there are several third party libraries you can use to do this: May 25, 2025 · This document covers the core property validation infrastructure in FluentValidation, including the IPropertyValidator interface, PropertyValidator base class, and the various specialized validator implementations. When you need to create a validation rule that depends on multiple properties of an object, you can achieve this by defining custom rules using the RuleFor method in combination with custom validation logic. Unfortunately this doesn't generalize very well due to FluentAssertions' design, so you might have to provide multiple overloads of this method with different types in place of MyClass. This works for me: Step up your . janacj julno pozpezhi csvhitq tyftn vojlz ylomn lvqiqg vzzlvj qeuc qoqfwbd ezeew kojav zoxty csgkova