Catalog / Primitives / make-type-partial

Make Type Partial

Adds the partial modifier to a class, struct, record or interface, so its members can be spread over several declarations.

Arguments

None. The target is the type, by symbol.

Precondition

The type is a class, struct, record, record struct or interface. Enums and delegates cannot be partial.
The type is not already partial.

Transformation

partial is added as the last modifier, immediately before the class, struct, record or interface keyword, where C# requires it.
A declaration with no modifiers gets partial in front of its keyword, after its attributes, documentation comment and any comment above it.
A containing type is left alone: a nested type can be partial on its own.

Preserved

The type's meaning: a single partial declaration compiles to the same type.
Attributes, comments, documentation, type parameters and constraints.

Limitations

No new part is created; adding members in another file is a separate step, such as Move Member to Another Partial File.

Error codes

Code	Meaning
`already-partial`	the type is already declared partial
`unsupported-type-kind`	the type is an enum or a delegate

Cases

Diffs show each file from before to after. /*[*/ … /*]*/ marks a selection and /*^*/ a caret; the runner removes them before the refactoring runs.

#already-partial-rejected

Refuses a type that is already partial

refusal

Targetsymbol T:Shop.Order

Refusesalready-partial; every file is left unchanged

Order.csinput

View fixture on GitHub

#enum-rejected

Refuses an enum, which cannot be partial

refusal

Targetsymbol T:Shop.Status

Refusesunsupported-type-kind; every file is left unchanged

Status.csinput

View fixture on GitHub

#generic-struct

Adds partial to a generic readonly struct with a constraint

success

Targetsymbol T:Shop.Range`1

Range.csmodified

View fixture on GitHub

#interface-implemented-in-another-file

Adds partial to an interface, leaving the class that implements it in another file unchanged

success

Targetsymbol T:Shop.IPricing

IPricing.csmodified

FlatPricing.csunchanged

View fixture on GitHub

#nested-record

Adds partial to a nested record, leaving the containing class as it is

success

Targetsymbol T:Shop.Catalogue.Entry

Catalogue.csmodified

View fixture on GitHub

#no-modifiers-with-documentation

Adds partial to a class with no modifiers, after its documentation comment, attribute and comment

success

Targetsymbol T:Shop.Basket

Basket.csmodified

View fixture on GitHub

#sealed-class

Adds partial after the other modifiers of a sealed class

success

Targetsymbol T:Shop.Invoice

Invoice.csmodified

View fixture on GitHub

1		namespace Shop;
2
3		public enum Status
4		{
5		Open,
6		Closed,
7		}

1	1		using System;
2	2
3	3		namespace Shop;
4	4
5		−	public readonly struct Range<T> where T : IComparable<T>
	5	+	public readonly partial struct Range<T> where T : IComparable<T>
6	6		{
7	7		public Range(T low, T high)
8	8		{
9	9		Low = low;
10	10		High = high;
11	11		}
12	12
13	13		public T Low { get; }
14	14
15	15		public T High { get; }
16	16		}

1	1		namespace Shop;
2	2
3		−	internal interface IPricing
	3	+	internal partial interface IPricing
4	4		{
5	5		decimal Price(string sku);
6	6		}

1	1		namespace Shop;
2	2
3	3		public class Catalogue
4	4		{
5		−	public record Entry(string Sku, decimal Price);
	5	+	public partial record Entry(string Sku, decimal Price);
6	6
7	7		public Entry First() => new Entry("A1", 2m);
8	8		}

1	1		using System;
2	2
3	3		namespace Shop
4	4		{
5	5		/// <summary>The items a customer is about to buy.</summary>
6	6		[Serializable]
7	7		// Kept small on purpose.
8		−	class Basket
	8	+	partial class Basket
9	9		{
10	10		public int Count;
11	11		}
12	12		}

1		namespace Shop;
2
3		public partial class Order
4		{
5		public int Id { get; set; }
6		}

1	1	namespace Shop;
2	2
3	3	internal class FlatPricing : IPricing
4	4	{
5	5	public decimal Price(string sku) => 1m;
6	6	}

1	1		namespace Shop;
2	2
3		−	public sealed class Invoice
	3	+	public sealed partial class Invoice
4	4		{
5	5		public decimal Total { get; set; }
6	6		}