C#: Given src => src.property, code choosing property if you have a string "propertyname"?

Question

I am using AutoMapper where it has:

.ForMember( dest => dest.id, opt => opt.MapFrom(src => src.id))

Using the far right expression src => src.id, if I have a string variable with the property's name, how would I choose the property by it?

I tried this:

src => propertyName

Then had to laugh when the value was "id".

Answer 1

If you have the name of the property you wish to access, you would use reflection to get MemberInfo and then invoke the property from the MemberInfo.

src => src.GetType().GetProperty(propertyName).GetGetMethod().Invoke(src, new object[] {})

Of course, this tidbit assumes src has properties and that propertyName identifies a property on the object.

Answer 2

You can use reflection to get a property by name:

private R GetProperty<T, R>(T obj, string propertyName)
{
    PropertyInfo pi = obj.GetType().GetProperty(propertyName);
    return (R)pi.GetValue(obj, null);
}

Which you would use in AutoMapper like this:

.ForMember( dest => dest.id, opt => opt.MapFrom(src => GetProperty(src, propertyName)))