How to use SetValue of an Indexed Property in Reflection?

Question

I have a C# Converter method which convers generic lists with the use of reflection.

The problem occurs when I try to call the SetValue method of the Item's property, it throws the following inner exception (ArgumentOutOfRangeException):

Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index.

Here is my code:

internal class Program
{
    private static void Main()
    {
        List<ClassA> classA = new List<ClassA>();
        classA.Add(new ClassA { Data = "value1" });
        classA.Add(new ClassA { Data = "value2" });

        List<ClassB> classB = Converter<List<ClassA>, List<ClassB>>(classA);
    }

    public static TOut Converter<TIn, TOut>(TIn request)
    {
        var response = Activator.CreateInstance<TOut>();
        PropertyInfo propertyA = typeof(TIn).GetProperty("Item");
        PropertyInfo propertyB = typeof(TOut).GetProperty("Item");

        int count = (int)typeof(TIn).GetProperty("Count").GetValue(request);
        for (int i = 0; i < count; i++)
        {
            var value = propertyA.GetValue(request, new object[] { i });
            var b = CreateBFromA(propertyB, propertyA, value);
            propertyB.SetValue(response, b, new object[] { i });
        }

        return response;
    }

    private static object CreateBFromA(PropertyInfo propertyB, PropertyInfo propertyA, object value)
    {
        var b = Activator.CreateInstance(propertyB.PropertyType);
        object o = propertyA.PropertyType.GetProperty("Data").GetValue(value);
        propertyB.PropertyType.GetProperty("Data").SetValue(b, o);
        return b;
    }
}

internal class ClassA
{
    public string Data { get; set; }
}

internal class ClassB
{
    public string Data { get; set; }

    public object Other { get; set; }
}

This is a small example code of a bigger generic method (where I need to use reflection), so you can try and run it to regenerate the exception.

How to use the SetValue method to avoid this exception?

Answer 1

Here is my aproach to it:

public static TCollectionOut ConvertCollection<TCollectionIn, TCollectionOut, TIn, TOut>(TCollectionIn input)
        where TCollectionIn : IEnumerable<TIn>
        where TCollectionOut : ICollection<TOut>, new()
        where TOut : new()
    {
        var res = new TCollectionOut();

        foreach (dynamic item in input)
        {
            dynamic o = new TOut();
            ConvertItem(item, o);
            res.Add(o);
        }
        return res;
    }

    public static TCollectionOut ConvertCollectionMoreDynamic<TCollectionIn, TCollectionOut>(TCollectionIn input)
        where TCollectionIn : IEnumerable

    {
        dynamic res = Activator.CreateInstance(typeof (TCollectionOut));

        var oType = typeof (TCollectionOut).GetMethod("Add").GetParameters().Last().ParameterType;

        foreach (dynamic item in input)
        {
            dynamic o = Activator.CreateInstance(oType);
            ConvertItem(item, o);
            res.Add(o);
        }
        return res;
    }

    public static void ConvertItem(ClassA input, ClassB output)
    {
        output.Data = input.Data;
    }

If you wich to support more types just create ConvertItem method with correct overload.

Answer 2

This is because you are trying to pass an index to a not indexed property (Data).

If you post the ClassA code I can try yo help. Anyway you can use LINQ to perform this kind of conversions. It's faster (to write and to execute) and type safe.