Question

What is the best way to go about this in C#?

string propPath = "ShippingInfo.Address.Street";

I’ll have a property path like the one above read from a mapping file.
I need to be able to ask the Order object what the value of the code below will be.

this.ShippingInfo.Address.Street 

Balancing performance with elegance. All object graph relationships should be one-to-one.
Part 2: how hard would it be to add in the capability for it to grab the first one if its a List<> or something like it.

Answer 1

Perhaps something like this?

string propPath = "ShippingInfo.Address.Street";

object propValue = this;
foreach (string propName in propPath.Split('.'))
{
    PropertyInfo propInfo = propValue.GetType().GetProperty(propName);
    propValue = propInfo.GetValue(propValue, null);
}

Console.WriteLine("The value of " + propPath + " is: " + propValue);

Or, if you prefer LINQ, you could try this instead. (Although I personally prefer the non-LINQ version.)

string propPath = "ShippingInfo.Address.Street";

object propValue = propPath.Split('.').Aggregate(
    (object)this,
    (value, name) => value.GetType().GetProperty(name).GetValue(value, null));

Console.WriteLine("The value of " + propPath + " is: " + propValue);