LINQ GroupBy with Dynamic Key Selection Causing Unexpected Results in C#
I'm trying to dynamically group a collection of objects using LINQ based on a property that I determine at runtime. My collection consists of a list of `Person` objects, and I want to group them by either `City` or `Age` depending on user input. However, I'm encountering unexpected results when I try to do this. The grouping seems to be inconsistent, and sometimes I get empty groups or groups that contain the wrong elements. Here's the relevant code snippet: ```csharp public class Person { public string Name { get; set; } public string City { get; set; } public int Age { get; set; } } var people = new List<Person> { new Person { Name = "Alice", City = "New York", Age = 30 }, new Person { Name = "Bob", City = "Los Angeles", Age = 25 }, new Person { Name = "Charlie", City = "New York", Age = 30 }, new Person { Name = "David", City = "Los Angeles", Age = 35 } }; string groupingCriteria = "City"; // this could be set to "Age" at runtime var groupedPeople = groupingCriteria == "City" ? people.GroupBy(p => p.City) : people.GroupBy(p => p.Age); foreach (var group in groupedPeople) { Console.WriteLine($"Group: {group.Key}"); foreach (var person in group) { Console.WriteLine($" - {person.Name}"); } } ``` When I run this code, I expect to see groups for each city with the respective people listed under them. However, when I switch `groupingCriteria` to `Age`, it seems to return empty groups or mixes people from different age groups. I checked that the data is populated correctly, but it feels like the `GroupBy` is not handling the keys as expected. What could be causing these unexpected results? Is there something I'm overlooking in the LINQ query? I'm using .NET 5.0. Any insights would be greatly appreciated!