c# - Linq 获取表中条目最多的员工的 ID

Question

我正在尝试编写一个 linq，它将返回表中条目最多的员工的 ID。

我的类(class)是这样的

public class TrainingEmployee
{
    public int EmployeeId { get; set; }
    public int TrainingId { get; set; }

    public List<TrainingEmployee> GenerateData()
    {
        return new List<TrainingEmployee>()
        {
            new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
            new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
            new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
            new TrainingEmployee() { EmployeeId = 1, TrainingId = 2},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 3},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 5},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 5},
            new TrainingEmployee() { EmployeeId = 2, TrainingId = 1},

        };
    }
}

这就是我的代码到目前为止的样子

var lista = new TrainingEmployee();

        var data = lista.GenerateData().GroupBy(x => x.EmployeeId);
        var maxValue = 0;
        var employeeId = 0;
        foreach (var group in data)
        {
            
            var currentlyGroupCount = group.Count();
            if(currentlyGroupCount > maxValue)
            {
                maxValue = currentlyGroupCount;
                employeeId = group.Key;
            }
        }
        Console.WriteLine("Value: {0} employeeid: {1}", maxValue, employeeId);
       

如何在不使用那么多代码的情况下仅在 linq 中完成上述代码？

Answer 1

您可以降序排列并选择第一个:

var employee = GenerateData()
    // group on EmployeeId
    .GroupBy(e => e.EmployeeId)
    // reverse order it on count
    .OrderByDescending(g => g.Count())
    // select the first
    .FirstOrDefault();

// check if the query returned anything other than default.
if(employee != default)
    Console.WriteLine("Value: {0} employeeid: {1}", employee.Count(), employee.EmployeeId);