C# linq 根据多字段动态Group by

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实现类： 

public static class LinqHepler
{/// <summary>/// 根据单个字段动态Group/// </summary>/// <typeparam name="T"></typeparam>/// <param name="source"></param>/// <param name="propertyName"></param>/// <returns></returns>public static IEnumerable<IGrouping<object, T>> GroupByDynamic<T>(this IEnumerable<T> source, string propertyName){var parameter = Expression.Parameter(typeof(T), "p");var property = Expression.Property(parameter, propertyName);var lambda = Expression.Lambda(typeof(Func<T, object>), Expression.Convert(property, typeof(object)), parameter);var groupByMethod = typeof(Enumerable).GetMethods().Where(m => m.Name == "GroupBy" && m.GetParameters().Length == 2).First();var groupBy = groupByMethod.MakeGenericMethod(typeof(T), typeof(object));return (IEnumerable<IGrouping<object, T>>)groupBy.Invoke(null, new object[] { source, lambda.Compile() });}/// <summary>/// 多字段动态GroupBy/// </summary>/// <typeparam name="T">需要重写GetHashCode和Equals方法， 因为类是比较引用的，而常用于GroupBy操作的匿名类的比较值的</typeparam>/// <param name="source"></param>/// <param name="propertyNames"></param>/// <returns></returns>public static IEnumerable<IGrouping<T, T>> GroupByDynamic<T>(this IEnumerable<T> source, List<string> propertyNames) where T : class{if(propertyNames.IsNullOrEmpty())throw new ArgumentNullException("propertyNames");var parameter = Expression.Parameter(typeof(T), "p");var lambda = BuildSelector<T>(parameter, propertyNames);var groupByMethod = typeof(Enumerable).GetMethods().Where(m => m.Name == "GroupBy" && m.GetParameters().Length == 2).First();var groupBy = groupByMethod.MakeGenericMethod(typeof(T), typeof(T));return (IEnumerable<IGrouping<T, T>>)groupBy.Invoke(null, new object[] { source, lambda });}private static Func<T, T> BuildSelector<T>(ParameterExpression param, List<string> propertyNames){var memberBindings = new List<MemberBinding>(propertyNames.Count);foreach (var propertyName in propertyNames){var expressionProperty = Expression.Property(param, propertyName);memberBindings.Add(Expression.Bind(typeof(T).GetProperty(propertyName), expressionProperty));}var memberInit = Expression.MemberInit(Expression.New(typeof(T)), memberBindings);var lambda = Expression.Lambda<Func<T, T>>(memberInit, param);return lambda.Compile();}
}

使用方式：

var people = new List<Person>
{new Person { Name = "Alice",Six="男", Age = 30 },new Person { Name = "Alice",Six="男", Age = 20 },new Person { Name = "Bob",Six="男", Age = 30 },new Person { Name = "Bob",Six="男", Age = 25 },new Person { Name = "Charlie",Six="男", Age = 25 },new Person { Name = "Charlie",Six="男", Age = 25 }
};var groupFileds = new List<string>() { "Name", "Six" };
var groupedByName = people.GroupByDynamic(groupFileds).Select(t =>{var model = new Person(){Name = t.First().Name,Six = t.First().Six,Age = t.Sum(p => p.Age),Details = t.ToList(),};return model;}).ToList();
//需要重写GetHashCode和Equals方法， 因为类是比较引用的，而常用于GroupBy操作的匿名类的比较值的
public class Person
{public string Name { get; set; }public string Six { get; set; }public int Age { get; set; }public List<Person> Details { get; set; }public override int GetHashCode(){return $"{Name},{Six},{Age}".GetHashCode(); //需要用来分组的字段，或者全部字段}public override bool Equals(object obj){var target = (Person)obj;return this.GetHashCode() == target.GetHashCode();}
}

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