The non generic BeEquivalentTo throws a NullReferenceException

Description

When using BeEquivalentTo on an implementation of System.Data.IDataParameterCollection (a non generic collection) containing a list of System.Data.SqlClient.SqlParameter a null reference exception is thrown

Complete minimal example reproducing the issue

//ARRANGE
var expected = new DataParameterCollection
{
	new SqlParameter{ParameterName = "Id", DbType = DbType.Int32, Value = 1},
};


//ACT
var subjectUnderTest = new DataParameterCollection
{
	new SqlParameter{ParameterName = "Id", DbType = DbType.Int32, Value = 1},
};

//ASSERT
subjectUnderTest.Should().BeEquivalentTo(expected);

Expected behavior:

The assertion should be true.

Actual behavior:

System.NullReferenceException: Object reference not set to an instance of an object. at System.Data.SqlClient.SqlParameter.get_IsNull()

Versions

.NET Core 2.1

Additional Information

class DataParameterCollection : IDataParameterCollection
{
	private readonly IList _list;

	public DataParameterCollection()
	{
		_list = new List<IDbDataParameter>(); // ArrayList or List<object> gives the same exception
	}
        // Adding this property and using it for the assertion instead solves the issue
	public IList<IDbDataParameter> InternalList => _list as IList<IDbDataParameter>;

	/// <inheritdoc />
	public IEnumerator GetEnumerator() => _list.GetEnumerator();

	/// <inheritdoc />
	public void CopyTo(Array array, int index) => _list.CopyTo(array, index);

	/// <inheritdoc />
	public int Count => _list.Count;

	/// <inheritdoc />
	public bool IsSynchronized => _list.IsSynchronized;

	public object SyncRoot => _list.SyncRoot;

	/// <inheritdoc />
	public int Add(object value) => _list.Add(value);

	/// <inheritdoc />
	public void Clear() => _list.Clear();


	/// <inheritdoc />
	public bool Contains(object value) => _list.Contains(value);

	/// <inheritdoc />
	public int IndexOf(object value) => _list.IndexOf(value);

	/// <inheritdoc />
	public void Insert(int index, object value) => _list.Insert(index, value);

	/// <inheritdoc />
	public void Remove(object value) => _list.Remove(value);

	/// <inheritdoc />
	public void RemoveAt(int index) => _list.RemoveAt(index);

	/// <inheritdoc />
	public bool IsFixedSize => _list.IsFixedSize;

	/// <inheritdoc />
	public bool IsReadOnly => _list.IsReadOnly;

	/// <inheritdoc />
	public object this[int index]
	{
		get => _list[index];
		set => _list[index] = value;
	}

	/// <inheritdoc />
	public bool Contains(string parameterName) => _list.Cast<IDbDataParameter>().SingleOrDefault(p => p.ParameterName.Equals(parameterName)) != null;

	/// <inheritdoc />
	public int IndexOf(string parameterName) =>
		_list.IndexOf(_list.Cast<IDbDataParameter>().SingleOrDefault(p => p.ParameterName.Equals(parameterName)));

	/// <inheritdoc />
	public void RemoveAt(string parameterName) => _list.RemoveAt(IndexOf(parameterName));

	/// <inheritdoc />
	public object this[string parameterName]
	{
		get => _list.Cast<IDbDataParameter>().SingleOrDefault(p => p.ParameterName.Equals(parameterName));
		set => throw new NotImplementedException();
	}
}

Exception message

   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
   at FluentAssertions.Equivalency.EquivalencyValidationContextExtentions.CreateForNestedMember(IEquivalencyValidationContext context, SelectedMemberInfo nestedMember, SelectedMemberInfo matchingProperty) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EquivalencyValidationContextExtentions.cs:line 14
   at FluentAssertions.Equivalency.StructuralEqualityEquivalencyStep.Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\StructuralEqualityEquivalencyStep.cs:line 46
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEqualityUsing(IEquivalencyValidationContext context) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 85
   at FluentAssertions.Equivalency.EnumerableEquivalencyValidator.TryToMatch[T](Object subject, T expectation, Int32 expectationIndex) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EnumerableEquivalencyValidator.cs:line 132
   at FluentAssertions.Equivalency.EnumerableEquivalencyValidator.LooselyMatchAgainst[T](IList`1 subjects, T expectation, Int32 expectationIndex) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EnumerableEquivalencyValidator.cs:line 103
   at FluentAssertions.Equivalency.EnumerableEquivalencyValidator.AssertElementGraphEquivalency[T](Object[] subjects, T[] expectations) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EnumerableEquivalencyValidator.cs:line 73
   at FluentAssertions.Equivalency.EnumerableEquivalencyValidator.Execute[T](Object[] subject, T[] expectation) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EnumerableEquivalencyValidator.cs:line 40
   at FluentAssertions.Equivalency.EnumerableEquivalencyStep.Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EnumerableEquivalencyStep.cs:line 45
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEqualityUsing(IEquivalencyValidationContext context) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 85
   at FluentAssertions.Equivalency.EquivalencyValidator.AssertEquality(EquivalencyValidationContext context) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Equivalency\EquivalencyValidator.cs:line 38
   at FluentAssertions.Collections.NonGenericCollectionAssertions.BeEquivalentTo(IEnumerable expectation, String because, Object[] becauseArgs) in C:\projects\fluentassertions-vf06b\Src\FluentAssertions\Collections\NonGenericCollectionAssertions.cs:line 326
   at Anon.ClassName.BeEquivalantTo_NonGenericList_ShouldNotThrow() in C:\Code\Fluent\src\Project\ClassName.cs:line 10

[jnyrup]

@Toudahl A much prettier approach for you would be to combine Including()/Excluding() and WhichGetterHas()/WhichGetterDoesNotHave().

subjectUnderTest.Should().BeEquivalentTo(expected,
    opt => opt.Excluding(ctx => ctx.WhichGetterHas(CSharpAccessModifier.Internal)));

subjectUnderTest.Should().BeEquivalentTo(expected,
    opt => opt.Excluding(ctx => ctx.WhichGetterDoesNotHave(CSharpAccessModifier.Public)));

subjectUnderTest.Should().BeEquivalentTo(expected, 
    opt => opt.Including(ctx => ctx.WhichGetterHas(CSharpAccessModifier.Public)));

subjectUnderTest.Should().BeEquivalentTo(expected, 
    opt => opt.Including(ctx => ctx.WhichGetterDoesNotHave(CSharpAccessModifier.Internal)));

[Toudahl]

I must have made a mistake when i tried it earlier today. It does indeed work as you say.