Round #808

Find the date with the highest number of new signups in a users table.

```csharp using System; using System.Collections.Generic; using System.Linq; public class User { public string Name { get; set; } public DateTime SignupDate { get; set; } } class Program { static void Main() { var users = new List<User> { new User { Name = "John", SignupDate = DateTime.Parse("2022-01-01") }, new User { Name = "Jane", SignupDate = DateTime.Parse("2022-01-01") }, new User { Name = "Alice", SignupDate = DateTime.Parse("2022-01-02") }, new User { Name = "Bob", SignupDate = DateTime.Parse("2022-01-03") }, new User { Name = "Charlie", SignupDate = DateTime.Parse("2022-01-03") }, new User { Name = "Dave", SignupDate = DateTime.Parse("2022-01-03") }, }; var signupCounts = users.GroupBy(u => u.SignupDate) .OrderByDescending(g => g.Count()) .FirstOrDefault(); Console.WriteLine($"The date with the highest number of new signups is: {signupCounts.Key.ToString("yyyy-MM-dd")}"); } } ```

```csharp using System; using System.Collections.Generic; using System.Linq; public class User { public DateTime SignupDate { get; set; } } public class Program { public static DateTime FindDateWithMostSignups(List<User> users) { if (users == null || users.Count == 0) { throw new ArgumentException("Users list is empty"); } var signupCounts = users .GroupBy(u => u.SignupDate.Date) .OrderByDescending(g => g.Count()) .FirstOrDefault(); return signupCounts.Key; } public static void Main(string[] args) { var users = new List<User> { new User { SignupDate = DateTime.Parse("2022-01-01") }, new User { SignupDate = DateTime.Parse("2022-01-01") }, new User { SignupDate = DateTime.Parse("2022-01-02") }, new User { SignupDate = DateTime.Parse("2022-01-03") }, new User { SignupDate = DateTime.Parse("2022-01-03") }, new User { SignupDate = DateTime.Parse("2022-01-03") }, }; var dateWithMostSignups = FindDateWithMostSignups(users); Console.WriteLine(dateWithMostSignups); } } ``` This code defines a `User` class with a `SignupDate` property and a `FindDateWithMostSignups` method that takes a list of `User` objects and returns the date with the highest number of new signups. The `Main` method demonstrates how to use this method with a sample list of users. The date with the most signups is then printed to the console. This implementation requires additional text to explain the code and its usage.