LINQ: left join

ffrom p in products
join c in categories on p.CategoryId equals c.Id into g
from c in g.DefaultIfEmpty()
select new
{
 CategoryTitle = c == null ? string.Empty : c.Title,
 ProductTitle = p.Title
};

View LINQ Generated SQL

Write class:

public class LinqDebugger : System.IO.TextWriter
{
  static readonly LinqDebugger _instance = new LinqDebugger();
  static readonly string _separator = new String('_', 150);

  public static LinqDebugger Instance { get { return _instance; } }

  private LinqDebugger()
  {
  }

  public override void WriteLine(string value)
  {
    System.Diagnostics.Debug.WriteLine(value);
    if (!string.IsNullOrEmpty(value) && value.StartsWith("-- Context:"))
    System.Diagnostics.Debug.WriteLine(_separator);
  }

  public override System.Text.Encoding Encoding
  {
   get { throw new NotImplementedException(); }
  }
}

Use:

  var db = new DBDataContext();
  db.Log = LinqDebugger.Instance;

VS output:

Linq Paging Extensions

public static class PagingExtensions
{
 //linq to sql
 public static IQueryable Page(this IQueryable source, int page, int size)
 {
  return source.Skip((page - 1) * size).Take(size);
 }

 //linq to objects
 public static IEnumerable Page(this IEnumerable source, int page, int size)
 {
  return source.Skip((page - 1) * size).Take(size);
 }
}

Select Top n Random Items

class Item
{
 public string Name { get; set; }
}
...
var list = new List { 
 new Item() { Name="Item1" },
 new Item() { Name="Item2" },
 new Item() { Name="Item3" },
 new Item() { Name="Item4" },
 new Item() { Name="Item5" },
};

Random rnd = new Random();

var items = from i in list
 orderby rnd.Next()
 select i;

var top = items.Take(3);