m пытается сгенерировать следующий запрос LINQ:

//Query the database for all AdAccountAlerts that haven't had notifications sent out
//Then get the entity (AdAccount) the alert pertains to, and find all accounts that
//are subscribing to alerts on that entity.
var x = dataContext.Alerts.Where(a => a.NotificationsSent == null)
  .OfType()
  .ToList()
  .GroupJoin(dataContext.AlertSubscriptions,
    a => new Tuple(a.AdAccountId, typeof(AdAccount).Name),
    s => new Tuple(s.EntityId, s.EntityType),
    (Alert, Subscribers) => new Tuple (Alert, Subscribers))
  .Where(s => s.Item2.Any())
  .ToDictionary(kvp => (Alert)kvp.Item1, kvp => kvp.Item2.Select(s => s.Username));

Использование деревьев выражений (что, кажется, единственный способ сделать это, когда мне нужно использовать типы отражений и времени выполнения). Обратите внимание, что в реальном коде (см. Ниже) AdAccountAlert на самом деле динамичен за счет отражения и цикла for.

Моя проблема: Я могу сгенерировать все до предложения .Where (). Вызов метода whereExpression разрывается из-за несовместимых типов. Обычно я знаю, что там делать, но вызов метода Any () меня смущает. Я'Я пробовал каждый тип, о котором только могу подумать, и не повезло. Любая помощь с обоими .Where () и .ToDictionary () будет принята с благодарностью.

Вот'Что я имею до сих пор:

var alertTypes = AppDomain.CurrentDomain.GetAssemblies()
  .Single(a => a.FullName.StartsWith("Alerts.Entities"))
  .GetTypes()
  .Where(t => typeof(Alert).IsAssignableFrom(t) && !t.IsAbstract && !t.IsInterface);

var alertSubscribers = new Dictionary();

//Using tuples for joins to keep everything strongly-typed
var subscribableType = typeof(Tuple);
var doubleTuple = Type.GetType("System.Tuple`2, mscorlib", true);

foreach (var alertType in alertTypes)
{
  Type foreignKeyType = GetForeignKeyType(alertType);
  if (foreignKeyType == null)
    continue;

  IQueryable unnotifiedAlerts = dataContext.Alerts.Where(a => a.NotificationsSent == null);

  //Generates: .OfType()
  MethodCallExpression alertsOfType = Expression.Call(typeof(Enumerable).GetMethod("OfType").MakeGenericMethod(alertType), unnotifiedAlerts.Expression);

  //Generates: .ToList(), which is required for joins on Tuples
  MethodCallExpression unnotifiedAlertsList = Expression.Call(typeof(Enumerable).GetMethod("ToList").MakeGenericMethod(alertType), alertsOfType);

  //Generates: a => new { a.{EntityId}, EntityType = typeof(AdAccount).Name }
  ParameterExpression alertParameter = Expression.Parameter(alertType, "a");
  MemberExpression adAccountId = Expression.Property(alertParameter, alertType.GetProperty(alertType.GetForeignKeyId()));
  NewExpression outerJoinObject = Expression.New(subscribableType.GetConstructor(new Type[] { typeof(int), typeof(string)}), adAccountId, Expression.Constant(foreignKeyType.Name));
  LambdaExpression outerSelector = Expression.Lambda(outerJoinObject, alertParameter);

  //Generates: s => new { s.EntityId, s.EntityType }
  Type alertSubscriptionType = typeof(AlertSubscription);
  ParameterExpression subscriptionParameter = Expression.Parameter(alertSubscriptionType, "s");
  MemberExpression entityId = Expression.Property(subscriptionParameter, alertSubscriptionType.GetProperty("EntityId"));
  MemberExpression entityType = Expression.Property(subscriptionParameter, alertSubscriptionType.GetProperty("EntityType"));
  NewExpression innerJoinObject = Expression.New(subscribableType.GetConstructor(new Type[] { typeof(int), typeof(string) }), entityId, entityType);
  LambdaExpression innerSelector = Expression.Lambda(innerJoinObject, subscriptionParameter);

  //Generates: (Alert, Subscribers) => new Tuple(Alert, Subscribers)
  var joinResultType = doubleTuple.MakeGenericType(new Type[] { alertType, typeof(IEnumerable) });
  ParameterExpression alertTupleParameter = Expression.Parameter(alertType, "Alert");
  ParameterExpression subscribersTupleParameter = Expression.Parameter(typeof(IEnumerable), "Subscribers");
  NewExpression joinResultObject = Expression.New(
    joinResultType.GetConstructor(new Type[] { alertType, typeof(IEnumerable) }),
    alertTupleParameter,
    subscribersTupleParameter);

  LambdaExpression resultsSelector = Expression.Lambda(joinResultObject, alertTupleParameter, subscribersTupleParameter);

  //Generates:
  //  .GroupJoin(dataContext.AlertSubscriptions,
  //    a => new { a.AdAccountId, typeof(AdAccount).Name },
  //    s => new { s.EntityId, s.EntityType },
  //    (Alert, Subscribers) => new Tuple(Alert, Subscribers))
  IQueryable alertSubscriptions = dataContext.AlertSubscriptions.AsQueryable();
  MethodCallExpression joinExpression = Expression.Call(typeof(Enumerable),
    "GroupJoin",
    new Type[]
    {
      alertType,
      alertSubscriptions.ElementType,
      outerSelector.Body.Type,
      resultsSelector.ReturnType
    },
    unnotifiedAlertsList,
    alertSubscriptions.Expression,
    outerSelector,
    innerSelector,
    resultsSelector);

  //Generates: .Where(s => s.Item2.Any())
  ParameterExpression subscribersParameter = Expression.Parameter(resultsSelector.ReturnType, "s");
  MemberExpression tupleSubscribers = Expression.Property(subscribersParameter, resultsSelector.ReturnType.GetProperty("Item2"));
  MethodCallExpression hasSubscribers = Expression.Call(typeof(Enumerable),
    "Any",
    new Type[] { alertSubscriptions.ElementType },
    tupleSubscribers);
  LambdaExpression whereLambda = Expression.Lambda(hasSubscribers, subscriptionParameter);
  MethodCallExpression whereExpression = Expression.Call(typeof(Enumerable),
    "Where",
    new Type[] { joinResultType },
    joinExpression,
    whereLambda);