AgileMapper matches nested members to source members with flattened names as you'd expect, but it also has a dedicated .Unflatten() API which unflattens objects in various ways. It is accessible:

• Via the static API, using Mapper.Unflatten(myObject)
• Via the instance API, using myInstanceMapper.Unflatten(myObject)
• Via an extension method, using myObject.Unflatten()

Unflattening produces an object populated using the source's flattened members.

For example, this Dictionary:

var dictionary = new Dictionary<string, object>
{
    ["Name"] = "Mrs Customer"
    ["Dob"] = new DateTime(1985, 11, 05),
    ["Address.Line1"] = "1 Street"
    ["Address.Postcode"] = "XY3 8HW"
};

...and the QueryString object created from this string-formatted string:

var queryString = 
     "Name=Mrs%20Customer" +
    "&Dob=11%2F5%2F1985%2012%3A00%3A00%20AM" +
    "&Address%2ELine1=1%20Street" +
    "&Address%2EPostcode=XY3%208HW"
    .ToQueryString(); // <- Creates a QueryString object

...can both be unflattened to this Customer object:

var customer = new Customer
{
    Name = "Mrs Customer",
    Dob = new DateTime(1985, 11, 05),
    Address = new Address
    {
        Line1 = "1 Street",
        Postcode = "XY3 8HW"
    }
};

...using Mapper.Unflatten(dictionary).To<Customer>(), or queryString.Unflatten().To<Customer>(), for example.