Sealed Modifier on Record ToString

• You can add the sealed modifier when you override ToString in a record type.
• Sealing the ToString method prevents the compiler from synthesizing a ToString method for any derived record types.
• A sealed ToString ensures all derived record types use the ToString method defined in a common base record type and have a consistent string representation throughout a hierarchy of record types.
• Derived records will still have a PrintMembers method generated for all derived properties.

Compiler Generated ToString and PrintMembers

The compiler synthesizes a virtual PrintMembers method and a ToString override to display the names and values of public properties and fields.

public record Person(string FirstName, string LastName, string[] PhoneNumbers);
Person person1 = new("George", "Washington", new string[] {"123456789"});
Console.WriteLine(person1);
//Output - Person { FirstName = George, LastName = Washington, PhoneNumbers = System.String[] }		

Derived Records

public abstract record Person(string FirstName, string LastName);
public record Teacher(string FirstName, string LastName, int Grade)
    : Person(FirstName, LastName);
public record Student(string FirstName, string LastName, int Grade)
    : Person(FirstName, LastName);

public static void Main()
{
    Person teacher = new Teacher("Nancy", "Davolio", 3);
    Console.WriteLine(teacher);
    // output: Teacher { FirstName = Nancy, LastName = Davolio, Grade = 3 }
}

Sealed ToString Method

ToString method is sealed in Person record. Derived record like Teacher can't override

public abstract record Person(string FirstName, string LastName)
{
	public sealed override string ToString()
	{
		StringBuilder stringBuilder = new StringBuilder();
		stringBuilder.Append("Base Record"); // type name
		stringBuilder.Append(" { ");
		if (PrintMembers(stringBuilder))
		{
			stringBuilder.Append(" ");
		}
		stringBuilder.Append("}");
		return stringBuilder.ToString();
	}
}
public record Teacher(string FirstName, string LastName, int Grade): Person(FirstName, LastName) 
{
	//Compiler error
	//Cannot override
	public override string ToString()
	{
		
	}
}

Example