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[Version 10.0] Feature support for record with sealed ToString #1550

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[Version 10.0] Feature support for record with sealed ToString #1550

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b811584
support record with sealed ToString
RexJaeschke Jan 24, 2026
bf362d7
Modify sealed record `ToString` rules
BillWagner Oct 28, 2026
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34 changes: 32 additions & 2 deletions standard/classes.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6325,13 +6325,15 @@ If the record class has no printable members, the method shall call the base `Pr

The `PrintMembers` method may be declared explicitly. It is an error if the explicit declaration does not match the expected signature or accessibility, or if the explicit declaration doesn't allow overriding it in a derived type and the record class type is not sealed.

The record class shall include a provided method method declared as follows:
Unless a base record class declares a sealed override of `object.ToString()`, the record class shall include a provided method declared as follows:

```csharp
public override string ToString();
```

The method may be declared explicitly. It is an error if the explicit declaration does not match the expected signature or accessibility, or if the explicit declaration doesn't allow overriding it in a derived type and the record class type is not sealed. It is an error if either provided, or explicitly declared, method doesn't override `object.ToString()` (for example, due to shadowing in intermediate base types).
The method may be declared explicitly. When no base record class declares a sealed override of `object.ToString()`, it is an error if the explicit declaration does not match the expected signature or accessibility, or if either the provided or explicitly declared method doesn't override `object.ToString()` (for example, due to shadowing in intermediate base types).

When a base record class declares a sealed override of `object.ToString()`, the implementation shall not provide a `ToString` method for the derived record class. An explicitly declared `ToString` member in such a derived record class is subject to the ordinary rules for member hiding and overriding. Sealing `ToString` does not prevent the implementation from providing `PrintMembers`.

The provided method:

Expand All @@ -6341,6 +6343,34 @@ The provided method:
1. Appends `}`,
1. Returns the builder's contents with `builder.ToString()`.

> *Example*: An unsealed record class can seal its `ToString` override. A derived record class inherits that implementation instead of receiving a provided override:
>
> <!-- Example: {template:"standalone-console", name:"PrintingMembers4", inferOutput:true} -->
> ```csharp
> record Base
> {
> public sealed override string ToString() => "Base";
> }
>
> record Derived(int Value) : Base;
>
> class Program
> {
> static void Main()
> {
> Console.WriteLine(new Derived(1));
> }
> }
> ```
>
> The output is:
>
> ```console
> Base
> ```
>
> *end example*
>
> *Example*: Given the following:
>
> <!-- Example: {template:"standalone-console", name:"PrintingMembers1", inferOutput:true} -->
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