Additional overload of SetValidator that accepts the propertyvalue.

Changelog.txt

@@ -20,6 +20,7 @@ Added Slovenian translations of default error messages.
 Added WithMessageArgument to the test helpers.
 Transform can now be used to transform property values to other types.
 FluentValidationModelValidatorProvider and FluentValidationModelValidator are now public.
+Add additional overload of SetValidator that takes a Func that receives the current property value.
 
 8.6.0 - 4 December 2019
 Add support for ASP.NET Core 3.1

src/FluentValidation.Tests/CollectionValidatorWithParentTests.cs

@@ -236,6 +236,26 @@ public class CollectionValidatorWithParentTests {
 			results.Errors[0].PropertyName.ShouldEqual("test[0].Surname");
 		}
 
+		[Fact]
+		public void Creates_validator_using_context_from_property_value() {
+			var personValidator = new InlineValidator<Person>();
+
+			var normalOrderValidator = new InlineValidator<Order>();
+			normalOrderValidator.RuleFor(x => x.Amount).GreaterThan(0);
+
+			var freeOrderValidator = new InlineValidator<Order>();
+			freeOrderValidator.RuleFor(x => x.Amount).Equal(0);
+
+			personValidator.RuleForEach(x => x.Orders)
+				.SetValidator((p, order) => order.ProductName == "FreeProduct" ? freeOrderValidator : normalOrderValidator);
+
+			var result1 = personValidator.Validate(new Person() {Orders = new List<Order> {new Order {ProductName = "FreeProduct"}}});
+			result1.IsValid.ShouldBeTrue();
+
+			var result2 = personValidator.Validate(new Person() {Orders = new List<Order> {new Order()}});
+			result2.IsValid.ShouldBeFalse();
+			result2.Errors[0].ErrorCode.ShouldEqual("GreaterThanValidator");
+		}
 
 		public class OrderValidator : AbstractValidator<Order> {
 			public OrderValidator(Person person) {

src/FluentValidation/FluentValidation.csproj

@@ -21,6 +21,8 @@ Changes in 9.0.0:
 * Translations of default error messages into other languages are now lazily-loaded
 * Added Slovenian translations of default error messages.
 * Added WithMessageArgument to the test helpers.
+* Add additional overload of SetValidator that takes a Func that receives the current property value.
+* ASP.NET Core: FluentValidationModelValidatorProvider and FluentValidationModelValidator are now public.
 
 Full release notes can be found at https://github.com/FluentValidation/FluentValidation/blob/master/Changelog.txt
 		</PackageReleaseNotes>

src/FluentValidation/Internal/RuleBuilder.cs

@@ -74,7 +74,7 @@ public class RuleBuilder<T, TProperty> : IRuleBuilderOptions<T, TProperty>, IRul
 		/// Sets the validator associated with the rule. Use with complex properties where an IValidator instance is already declared for the property type.
 		/// </summary>
 		/// <param name="validatorProvider">The validator provider to set</param>
-		/// <param name="ruleSet"></param>
+		/// <param name="ruleSets"></param>
 		public IRuleBuilderOptions<T, TProperty> SetValidator<TValidator>(Func<T, TValidator> validatorProvider, params string[] ruleSets)
 			where TValidator : IValidator<TProperty> {
 			validatorProvider.Guard("Cannot pass a null validatorProvider to SetValidator", nameof(validatorProvider));
@@ -84,6 +84,19 @@ public class RuleBuilder<T, TProperty> : IRuleBuilderOptions<T, TProperty>, IRul
 			return this;
 		}
 
+		/// <summary>
+		/// Associates a validator provider with the current property rule.
+		/// </summary>
+		/// <param name="validatorProvider">The validator provider to use</param>
+		/// <param name="ruleSets"></param>
+		public IRuleBuilderOptions<T, TProperty> SetValidator<TValidator>(Func<T, TProperty, TValidator> validatorProvider, params string[] ruleSets) where TValidator : IValidator<TProperty> {
+			validatorProvider.Guard("Cannot pass a null validatorProvider to SetValidator", nameof(validatorProvider));
+			SetValidator(new ChildValidatorAdaptor(context => validatorProvider((T) context.InstanceToValidate, (TProperty) context.PropertyValue), typeof (TValidator)) {
+				RuleSets = ruleSets
+			});
+			return this;
+		}
+
 		/// <summary>
 		/// Sets the validator associated with the rule. Use with complex properties where an IValidator instance is already declared for the property type.
 		/// </summary>

src/FluentValidation/Syntax.cs

@@ -68,6 +68,14 @@ public interface IRuleBuilder<T, out TProperty> {
 		/// <param name="ruleSets"></param>
 		IRuleBuilderOptions<T, TProperty> SetValidator<TValidator>(Func<T, TValidator> validatorProvider, params string[] ruleSets)
 			where TValidator : IValidator<TProperty>;
+
+		/// <summary>
+		/// Associates a validator provider with the current property rule.
+		/// </summary>
+		/// <param name="validatorProvider">The validator provider to use</param>
+		/// <param name="ruleSets"></param>
+		IRuleBuilderOptions<T, TProperty> SetValidator<TValidator>(Func<T, TProperty, TValidator> validatorProvider, params string[] ruleSets)
+			where TValidator : IValidator<TProperty>;
 	}