What steps will reproduce the problem? 1. i'm trying to write the mock unit test for my WIA implementation. After reference the WIA component, the visual studio 2010 genereted these classes for me:

namespace WIA { [Guid("40571E58-A308-470A-80AA-FA10F88793A0")] [TypeLibType(4160)] public interface IProperties : IEnumerable { [DispId(1)] int Count {get; }

    [DispId(0)]
    Property this[ref object Index] {get; }

    [DispId(2)]
    bool Exists(ref object Index);
    [TypeLibFunc(1)]
    [DispId(-4)]
    IEnumerator GetEnumerator();
}

} namespace WIA { [CoClass(typeof(PropertiesClass))] [Guid("40571E58-A308-470A-80AA-FA10F88793A0")] public interface Properties : IProperties { } }

Properties is a collection of Property object, the collection is index by String; therefore, to mock the Properties object, i have

        var mockWIAProperties = new Mock<WIA.Properties>();
        mockWIAProperties.SetupGet(m => m[It.IsAny<String>()]).Returns(getMockWIAProperty());

And the getMockWIAProperty is:

    public static WIA.Property getMockWIAProperty()
    {
        var mockWIAProperty = new Mock<WIA.Property>();
        return mockWIAProperty.Object;
    }

2. 3.

What is the expected output? Should be no error at run time

What do you see instead? failed: System.IndexOutOfRangeException : Index was outside the bounds of the array

What version of the product are you using? On what operating system? Moq - 4.0.10827.0

Please provide any additional information below.

I too get the same error "System.IndexOutOfRangeException: Index was outside the bounds of the array." when I mock Microsoft.Office.Interop.Word.Shapes and trying to setup

object mockintobj = 1; mockShapes.Setup(x => x[mockintobj]).Returns(mockShape.Object);

Here is the parameter expected by Microsoft.Office.Interop.Word.Shape indexer

Shape this[ref object Index] {get; }

Is there any fix scheduled in future?