As part of ongoing efforts to ensure type safety and reduce null reference exceptions, C# 11.0 introduces the required modifier.

This modifier can be applied to properties, fields, and parameters to indicate that they must be set by either an initializer or constructor.

Code

Now

public class NamedIdentity
{
    public required string Name { get; init; }
    public required Guid Identity { get; init; }

    [SetsRequiredAttributes]
    public NamedIdentity(string name, Guid identity)
    {
        Name = name;
        Identity = identity;
    }

    // No validation needed as the compiler will check that all
    // required parameter using this constructor have been set.
    public NamedIdentity()
    {
    }
}

Before

public class NamedIdentity
{
    public string Name { get; init; }
    public Guid Identity { get; init; }

    public NamedIdentity(string name, Guid identity)
    {
        Name = name;
        Identity = identity;
    }

    // If we want to allow initializer syntax we need this constructor.
    // Remember to validate all required values were set.
    public NamedIdentity()
    {
    }
}

Notes

• You can decorate a constructor with SetsRequiredMembers to indicate to the compiler that this constructor sets all required members

More information

• What's New in C# 11
• Language reference
• Required members and init accessor