SO76722226

_only.cs

void Main()
{
	GetItems(MathOperation.Average).Dump();
	GetItems(MathOperation.Max).Dump();
	GetItems(MathOperation.Min).Dump();
}

IEnumerable<Item> GetItems(MathOperation mathOperation)
{
	Expression<Func<IGrouping<long, Album>, decimal>> operation = mathOperation switch
	{
		MathOperation.Max => x => x.Max(y => y.AlbumId),
		MathOperation.Min => x => x.Min(y => y.AlbumId),
		MathOperation.Average => x => (decimal)x.Average(y => y.AlbumId),
		_ => throw new ArgumentOutOfRangeException(),
	};

	return Albums.GroupBy(a => a.ArtistId).AsExpandable().Select(x => new Item
	{
		Artist = x.Key,
		Something = operation.Invoke(x)
	});
}


enum MathOperation
{
	Max,
	Min,
	Average
}

class Item
{
	public long Artist { get; set; }
	public decimal Something { get; set; }
}

full.linq

<Query Kind="Program">
  <Connection>
    <ID>54bf9502-9daf-4093-88e8-7177c12aaaaa</ID>
    <NamingService>2</NamingService>
    <Persist>true</Persist>
    <Driver Assembly="(internal)" PublicKeyToken="no-strong-name">LINQPad.Drivers.EFCore.DynamicDriver</Driver>
    <AttachFileName>&lt;ApplicationData&gt;\LINQPad\ChinookDemoDb.sqlite</AttachFileName>
    <DisplayName>Demo database (SQLite)</DisplayName>
    <DriverData>
      <PreserveNumeric1>true</PreserveNumeric1>
      <EFProvider>Microsoft.EntityFrameworkCore.Sqlite</EFProvider>
      <MapSQLiteDateTimes>true</MapSQLiteDateTimes>
      <MapSQLiteBooleans>true</MapSQLiteBooleans>
    </DriverData>
  </Connection>
  <NuGetReference>LinqKit</NuGetReference>
  <Namespace>LinqKit</Namespace>
</Query>

void Main()
{
	GetItems(MathOperation.Average).Dump();
	GetItems(MathOperation.Max).Dump();
	GetItems(MathOperation.Min).Dump();
}

IEnumerable<Item> GetItems(MathOperation mathOperation)
{
	Expression<Func<IGrouping<long, Album>, decimal>> operation = mathOperation switch
	{
		MathOperation.Max => x => x.Max(y => y.AlbumId),
		MathOperation.Min => x => x.Min(y => y.AlbumId),
		MathOperation.Average => x => (decimal)x.Average(y => y.AlbumId),
		_ => throw new ArgumentOutOfRangeException(),
	};

	return Albums.GroupBy(a => a.ArtistId).AsExpandable().Select(x => new Item
	{
		Artist = x.Key,
		Something = operation.Invoke(x)
	});
}


enum MathOperation
{
	Max,
	Min,
	Average
}

class Item
{
	public long Artist { get; set; }
	public decimal Something { get; set; }
}