Get<T>()/Update() entity tracking changes and issues

[develax]

In the description of public static T Get<T>(...) method it's said that

"Entities created from interfaces are tracked/intercepted for changes and used by the Update() extension for optimal performance."

To check it I created an interface

public interface IInvoice
{
     string Code { get; set; }
     InvoiceDetail Detail { get; set; }
     [Key]
     int InvoiceID { get; set; }
     List<InvoiceItem> Items { get; set; }
     InvoiceKind Kind { get; set; }
}

for class Invoice : IInvoice and tried the next code:

using (var connection = ConnectionFactory())
{
     connection.Open();
     IInvoice invoice = connection.Get<IInvoice>(1);
     invoice.Code = "Bla bla bla";
     connection.Update(invoice);
}

First I got an exception

"Invalid cast from 'System.Int32 to InvoiceDetail." for which I've already made a pull-request.

After fixing it I got another exception at line 417 in SqlMapper.cs

System.NotSupportedException: 'The member Detail of type Z.Dapper.Examples.API.Dapper.Methods.InvoiceDetail cannot be used as a parameter value'

So, now the question is why does it check all the properties while I changed only one? Isn't it going to update them all?