Strange "Expected invocation on the mock at least once, but was never performed" error when I am setting up the Mock - vb.net

Question

I'm getting this error from Moq via NUnit, and it doesn't make much in the way of sense to me.
"Expected invocation on the mock at least once, but was never performed: x => x.DeleteItem(.$VB$Local_item)"
"at Moq.Mock.ThrowVerifyException(MethodCall expected, IEnumerable1 setups, IEnumerable1 actualCalls, Expression expression, Times times, Int32 callCount)
at Moq.Mock.VerifyCalls(Interceptor targetInterceptor, MethodCall expected, Expression expression, Times times)
at Moq.Mock.Verify[T](Mock mock, Expression1 expression, Times times, String failMessage)
at Moq.Mock1.Verify(Expression`1 expression)
at PeekABookEditor.UnitTests.ItemBrowsing.Can_Delete_Item() in C:\Projects\MyProject\MyProject.UnitTests\Tests\ItemBrowsing.vb:line 167"
Very similar code works well in C#, so the error might be minor and syntactical on my part.
Here's my code:
<Test()> _
Public Sub Can_Delete_Item()
'Arrange: Given a repository containing some item...
Dim mockRepository = New Mock(Of IItemsRepository)()
Dim item As New Item With {.ItemID = "24", .Title = "i24"}
mockRepository.Setup(Function(x) x.Items).Returns(New Item() {item}.AsQueryable())
'Act ... when the user tries to delete that product
Dim controller = New ItemsController(mockRepository.Object)
Dim result = controller.Delete(24)
'Assert ... then it's deleted, and the user sees a confirmation
mockRepository.Verify(Sub(x) x.DeleteItem(item))
result.ShouldBeRedirectionTo(New With {Key .action = "List"})
Assert.AreEqual(DirectCast(controller.TempData("message"), String), "i24 was deleted")
End Sub
The guilty line appears to be "mockRepository.Verify(Sub(x) x.DeleteItem(item))"
Any thoughts on how to fix this?
Working C# code isn't the exact same, but here it is:
[Test]
public void Can_Delete_Product()
{
// Arrange: Given a repository containing some product...
var mockRepository = new Mock<IProductsRepository>();
var product = new Product { ProductID = 24, Name = "P24"};
mockRepository.Setup(x => x.Products).Returns(
new[] { product }.AsQueryable()
);
// Act: ... when the user tries to delete that product
var controller = new AdminController(mockRepository.Object);
var result = controller.Delete(24);
// Assert: ... then it's deleted, and the user sees a confirmation
mockRepository.Verify(x => x.DeleteProduct(product));
result.ShouldBeRedirectionTo(new { action = "Index" });
controller.TempData["message"].ShouldEqual("P24 was deleted");
}

Answer 1

In your VB test method, you create Item with a string ItemID = "24", but you call the controller.Delete method with an integer value of 24.
Check your controller code and see if the type discrepancy results in the item not being identified correctly, so either DeleteItem is not called at all, or is called with a different Item.