Table of Contents

Copying

Tracking needs independent snapshots, an original to compare against, a state to revert to. Copy<T> makes one, with an IL-generated clone cached per type.

var snapshot = original.Copy();

The default is a member-wise (shallow) clone. Attributes opt individual fields into deeper behavior.

Field attributes

  • [Copy] clones the field with Copy<T> (deep for that field).
  • [ShallowCollection] clones the collection container, shares the elements.
  • [DeepCollection] clones the container and clones each element.
  • [CopyUsingMethod("Name")] calls a zero-argument instance method on the container and assigns its return value to the field.

Attributes are honored up the inheritance chain.

A mixed snapshot

An invoice whose snapshot must own its line items but may share the immutable customer:

public sealed class Invoice {
    public string Number = "";              // member-wise copy
    public Customer Customer = null!;       // shared reference, intentionally

    [DeepCollection]
    public List<InvoiceLine> Lines = [];    // new list, fresh line clones

    [Copy]
    public Address BillTo = null!;          // fresh Address
}

Invoice snapshot = invoice.Copy();

Custom clone logic

Implement ICopyable<T> to take over the whole clone for a type. For direct collection clones without a containing object, CollectionCopyExtensions offers shallow (shared elements) and deep (cloned elements) copies.

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