Diagnostics

Immediate.Validations ships seventeen diagnostics, all in the ImmediateValidations category and all enabled by default. IV0001–IV0010 police the custom validator contract; IV0011 checks the handler pipeline; IV0012–IV0018 check how validators are applied to your types.

Severity can be adjusted per project in .editorconfig:

[*.cs]
dotnet_diagnostic.IV0011.severity = none

Diagnostic reference

IV0001

A type deriving from ValidatorAttribute has no method named ValidateProperty. The generated code has nothing to call.

Fix: add public static bool ValidateProperty(…). The code fix Add ‘ValidateProperty’ method scaffolds one; it is offered on class declarations.

IV0002

ValidateProperty exists but is not static. Generated code calls it without an instance.

Fix: add the static modifier, or use the Make ‘ValidateProperty’ method static code fix.

IV0003

More than one static ValidateProperty overload was found on the validator. Overloads are not supported — the generator would not know which to bind.

Fix: collapse them into one method, using a generic parameter or optional parameters if you need flexibility.

IV0004

ValidateProperty does not return bool. true must mean the value is valid.

Fix: change the return type, or use the Correct ‘ValidateProperty’ return type code fix.

IV0005

The validator declares a constructor parameter or settable property with no matching ValidateProperty parameter. Matching is by name, case-insensitively. Reported on the offending property or parameter.

Fix: add the parameter to ValidateProperty, or remove the attribute member.

IV0006

The mirror image: ValidateProperty declares a parameter (other than the first) that has no matching constructor parameter or property on the validator, so nothing can ever supply a value for it.

Fix: add a constructor parameter or required property with that name, or remove the parameter.

IV0007

A matching pair exists, but the attribute member’s type is not assignable to the ValidateProperty parameter’s type. Reported twice — once on the parameter, once on the member.

Fix: align the types, or mark the attribute member [TargetType] if it is deliberately typed as object or string to accept the validated property’s type.

IV0008

A ValidateProperty parameter has no default value, but the attribute member that feeds it is optional — a property that is not required, or a constructor parameter with a default. The generated call would have no value to pass.

Fix: mark the property required and remove the constructor parameter’s default, or give the ValidateProperty parameter a default value.

IV0009

The validator declares two or more non-static constructors. Only one is supported. Reported once per constructor.

Fix: reduce to a single constructor, moving optional configuration to init-only properties.

IV0010

The validator has no public static string DefaultMessage property and no public const string DefaultMessage field. Without one there is no message to record on failure, and ValidationResult.Add(() => …) would throw at runtime.

Fix: add one. Read it from ValidationConfiguration.Localizer if you want it localizable.

IV0011

The assembly declares [assembly: Behaviors(...)] without ValidationBehavior<,> in the list, so validation targets in this assembly are generated but never executed by the handler pipeline.

Fix: add typeof(ValidationBehavior<,>) to the list — see Integrating with Immediate.Handlers.

IV0012

A type applies validator attributes to its properties, or declares IValidationTarget<T>, but is not marked [Validate]. Without the attribute the generator never sees it and no validation code is produced.

Fix: add [Validate], or use the Add [Validate] code fix.

IV0013

A validation target does not declare IValidationTarget<TSelf>. Validation code is still generated, but ValidationBehavior<,> and the generic ThrowIfInvalid overloads will not accept the type, because both are constrained on the interface.

Fix: add the interface, or use the Add IValidationTarget<T> code fix. Both support fix-all.

IV0014

A validator attribute was applied to a property whose type it cannot handle — [Length] on an int, for instance, or a custom validator whose generic constraints the property type does not satisfy. The attribute is silently dropped from the generated code, so this warning is the only signal that the rule is not running.

The diagnostic is tagged unnecessary, so IDEs fade the attribute out.

Fix: remove the attribute or change the property type.

IV0015

A value passed to a [TargetType] parameter or property does not have the required type — a string literal where the validated property is an int, or a nameof() reference to a member of the wrong type.

Fix: pass a value of the validated property’s type, or of the type the validator’s ValidateProperty parameter declares (int for the length validators, Regex for Match’s regex).

IV0016

Removed in release 2.3. It reported an invalid-type nameof() reference passed to a validator; that case is now covered by IV0015. No analyzer reports IV0016 any more, so suppressions for it can be deleted.

IV0017

A nameof() argument does not resolve to something usable: it names something that is not a property, field or method; it names an instance member of another type; or it names a member that does not exist on the validated type. The message states what the reference must refer to.

Fix: point the reference at a property, field or parameterless method on the validated type, or at a static member of another type.

IV0018

[NotNull] was applied to a property whose type is a non-nullable value type, where the check can never fail.

Fix: remove the attribute, or change the property type to Nullable<T> if the value really is optional.

Code fixes and refactorings

All five code fixes support batch fix-all. The refactoring is offered from the lightbulb menu on any [Validate] type that does not already declare an AdditionalValidations method.

Suppressors

Two DiagnosticSuppressors ship with the package to silence compiler and analyzer warnings that are false positives in this programming model.

CS0658 is “not a recognized attribute location”; suppressing it is what makes the element: syntax usable. CS9113 is “parameter is unread” and CA1019 is “define accessors for attribute arguments” — both are expected on validators, whose constructor parameters are consumed by generated code rather than by the attribute itself.