FluentValidation throws NullReferenceException when validation object is null

FluentValidation throws NullReferenceException when the object is null

Expected: ValidationResult with Message “Entity cannot be null”

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using FluentValidation;

namespace ConsoleApplication11
{
    public class Entity
    {
        public string Type { get; set; }
    }

    public class EntityValidator : AbstractValidator<Entity>
    {
        public EntityValidator()
        {
            this.RuleFor(a => a)
             .NotEmpty()
             .WithMessage("Entity cannot be null");


            this.RuleFor(a => a.Type)
                .NotEmpty()
                .WithMessage("Type cannot be null or empty");

        }
    }

    internal class Program
    {
        private static void Main(string[] args)
        {
            Entity entity = null;


            var validator = new EntityValidator();


            validator.Validate(entity);
        }
    }

}

Stacktrace:

   at lambda_method(Closure , Entity )
   at FluentValidation.Internal.Extensions.<>c__DisplayClass1`2.<CoerceToNonGeneric>b__0(Object x) in c:\Projects\FluentValidation\src\FluentValidation\Internal\Extensions.cs:line 108
   at FluentValidation.Validators.PropertyValidatorContext.get_PropertyValue() in c:\Projects\FluentValidation\src\FluentValidation\Validators\PropertyValidatorContext.cs:line 53
   at FluentValidation.Validators.PropertyValidator.Validate(PropertyValidatorContext context) in c:\Projects\FluentValidation\src\FluentValidation\Validators\PropertyValidator.cs:line 69
   at FluentValidation.Internal.PropertyRule.InvokePropertyValidator(ValidationContext context, IPropertyValidator validator, String propertyName) in c:\Projects\FluentValidation\src\FluentValidation\Internal\PropertyRule.cs:line 360
   at FluentValidation.Internal.PropertyRule.<Validate>d__10.MoveNext() in c:\Projects\FluentValidation\src\FluentValidation\Internal\PropertyRule.cs:line 241
   at System.Linq.Enumerable.<SelectManyIterator>d__1`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at FluentValidation.AbstractValidator`1.Validate(ValidationContext`1 context) in c:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 113
   at FluentValidation.AbstractValidator`1.Validate(T instance) in c:\Projects\FluentValidation\src\FluentValidation\AbstractValidator.cs:line 94
   at ConsoleApplication11.Program.Main(String[] args) in c:\users\administrator\documents\visual studio 2015\Projects\ConsoleApplication11\Program.cs:line 37
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

[ryanbuening]

Not being able to validate against null objects prevents me from using FV. I have nested classes in my ViewModel that can be null.

[theofanis]

@spawluk That’s the exact problem in my case. The bound model from the JSON payload, let’s say in a POST request, is null, so the validator never kicks in, so it needs a custom way to handle this case. Not pretty.