C#

db.Connection.Open();

Quote:

Behavior in EF6 and future versions

For EF6 and future versions we have taken the approach that if the calling code chooses to open the connection by calling context.Database.Connection.Open() then it has a good reason for doing so and the framework will assume that it wants control over opening and closing of the connection and will no longer close the connection automatically.

Note: This can potentially lead to connections which are open for a long time so use with care.

Quote:

You can use this property to interoperate with relational ADO.NET code.

The returned connection will be closed unless it has been explicitly opened by the user.

db.Connection.Open();

List<something> somename=new List<something>();

List<something> somename=new List<something>(someconstant);

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

namespace LargeObjectsHeapTester {
	//
	// This class collects a sequence of items of type T (value or reference type)
	// and keeps them in the order they get added.
	// A list-of-lists technique is used to keep everything in the regular heap,
	// i.e. this class should not challenge the large object heap unless
	// the number of items collected gets really big (above 100 million).
	// To control what is inside the collection:
	//	- use Add to add an item at the end;
	//	- use Clear to clear the collection.
	// To obtain information about its content:
	//	- use the Count property;
	//	- use the IEnumerable<T> interface (or the old-fashioned IEnumerable if you must)
	//	  (both foreach and LINQ rely on the IEnumerable<T> interface when present)
	//
	// Note: value types such as structs should be small (max 8B) otherwise
	// the level1 lists may not fit in the regular heap.
	public class ListOfLists<T> :IEnumerable, IEnumerable<T> {
		public const int MAX_ITEMS_IN_LEVEL1=10000;
		//public static ILog Logger;
		private List<List<T>> level0;
		private List<T> currentLevel1;

		// constructor
		public ListOfLists() {
			Clear();
		}

		// logging utility
		private void log(string msg) {
			//if(Logger!=null) Logger.log(msg);
		}

		// empty the collection
		public void Clear() {
			level0=new List<List<T>>();
			currentLevel1=new List<T>();
			level0.Add(currentLevel1);
		}

		// add an item at the end of the collection
		public void Add(T item) {
			if(currentLevel1.Count>=MAX_ITEMS_IN_LEVEL1) {
				currentLevel1=new List<T>();
				level0.Add(currentLevel1);
			}
			currentLevel1.Add(item);
		}

		// get the number of items in the collection
		public int Count {
			get {
				int totalCount=0;
				foreach(List<T> level1 in level0) totalCount+=level1.Count;
				return totalCount;
			}
		}

		// log the internals
		public void DumpCounts() {
			int totalCount=0;
			log("level0.Count="+level0.Count);
			int i=0;
			foreach(List<T> level1 in level0) {
				int count1=level1.Count;
				log("level0["+i+"].Count="+count1);
				totalCount+=count1;
				i++;
			}
			log("total count="+totalCount);
		}

		// get an old-style enumerator (typeless)
		IEnumerator IEnumerable.GetEnumerator() {
			return this.GetEnumerator();
		}

		// get an enumerator (this one gets used by foreach and LINQ)
		public IEnumerator<T> GetEnumerator() {
			foreach(List<T> level1 in level0) {
				foreach(T item in level1) {
					yield return item;
				}
			}
		}
	}
}

var allMailboxes = db.Users.Where(x ... ... ... ).ToList();                                              

List<MessageTrackingLog> totalSentLogs = sentLogs.Where(a => a.Users.Contains(x.EmailAddress, StringComparer.OrdinalIgnoreCase)).ToList();

IEnumerable<MessageTrackingLog> totalSentLogs=LINQ statement without .ToList();
int sentCount=0;
int sentBytes=0;
foreach(MessageTrackingLog item in totalSentLogs) {
    sentCount++;
    sentBytes+=item.TotalBytes;
}

return source
  .GroupBy(x => (ndx++ / chunksz))
  .Select(grp => new KeyValuePair<T1, List<T1>>(grp.First(), grp.Skip(1).ToList()));