public enum AlertSeverity { Warning, Critical }

public static class AlertSeverityExtensions
{
    public static string ToDbString(this AlertSeverity s) => s switch
    {
        AlertSeverity.Warning  => "WARNING",
        AlertSeverity.Critical => "CRITICAL",
        _ => throw new ArgumentOutOfRangeException(nameof(s))
    };

    public static AlertSeverity FromDbString(string v) => v switch
    {
        "WARNING"  => AlertSeverity.Warning,
        "CRITICAL" => AlertSeverity.Critical,
        _ => throw new ArgumentOutOfRangeException(nameof(v), $"Unknown alert severity: '{v}'")
    };
}