public class ArrayEnumerable<T> : IEnumerable<T>
    {
        T[] _array;
        public ArrayEnumerable(T[] array)
        {
            _array = array;
        }


        public IEnumerator<T> GetEnumerator()
        {
            int index = 0;
            while (index < _array.Length)
            {
                yield return _array[index];
                index++;
            }
            yield break;
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }

public class ArrayEnumerable<T> : IEnumerable<T>, IEnumerable
{
    // Fields
    private T[] _array;

    // Methods
    public ArrayEnumerable(T[] array)
    {
        this._array = array;
    }

    public IEnumerator<T> GetEnumerator()
    {
        return new <GetEnumerator>d__0(0);
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return this.GetEnumerator();
    }

    // Nested Types
    [CompilerGenerated]
    private sealed class <GetEnumerator>d__0 : IEnumerator<T>, IEnumerator, IDisposable
    {
        // Fields
        private int <>1__state;
        private T <>2__current;
        public ArrayEnumerable<T> <>4__this;
        public int <index>5__1;

        // Methods
        [DebuggerHidden]
        public <GetEnumerator>d__0(int <>1__state)
        {
            this.<>1__state = <>1__state;
        }

        private bool MoveNext()
        {
            switch (this.<>1__state)
            {
                case 0:
                    this.<>1__state = -1;
                    this.<index>5__1 = 0;
                    while (this.<index>5__1 < ArrayEnumerable<T>._array.Length)
                    {
                        this.<>2__current = ArrayEnumerable<T>._array[this.<index>5__1];
                        this.<>1__state = 1;
                        return true;
                    Label_0050:
                        this.<>1__state = -1;
                        this.<index>5__1++;
                    }
                    break;

                case 1:
                    goto Label_0050;
            }
            return false;
        }

        [DebuggerHidden]
        void IEnumerator.Reset()
        {
            throw new NotSupportedException();
        }

        void IDisposable.Dispose()
        {
        }

        // Properties
        T IEnumerator<T>.Current
        {
            [DebuggerHidden]
            get
            {
                return this.<>2__current;
            }
        }

        object IEnumerator.Current
        {
            [DebuggerHidden]
            get
            {
                return this.<>2__current;
            }
        }
    }
}

def array_iterator(array):
    length = len(array)
    index = 0
    while index < length:
        yield array[index]
        index = index + 1

>>> import dis
>>> dis.dis(array_iterator)
  2           0 LOAD_GLOBAL              0 (len)
              3 LOAD_FAST                0 (array)
              6 CALL_FUNCTION            1
              9 STORE_FAST               1 (length)

  3          12 LOAD_CONST               1 (0)
             15 STORE_FAST               2 (index)

  4          18 SETUP_LOOP              35 (to 56)
        >>   21 LOAD_FAST                2 (index)
             24 LOAD_FAST                1 (length)
             27 COMPARE_OP               0 (<)
             30 POP_JUMP_IF_FALSE       55

  5          33 LOAD_FAST                0 (array)
             36 LOAD_FAST                2 (index)
             39 BINARY_SUBSCR
             40 YIELD_VALUE
             41 POP_TOP

  6          42 LOAD_FAST                2 (index)
             45 LOAD_CONST               2 (1)
             48 BINARY_ADD
             49 STORE_FAST               2 (index)
             52 JUMP_ABSOLUTE           21
        >>   55 POP_BLOCK
        >>   56 LOAD_CONST               0 (None)
             59 RETURN_VALUE 

    public class SimpleStateMachine : IEnumerable<bool>
    {
        public IEnumerator<bool> GetEnumerator()
        {
            while (true)
            {
                yield return true;
                yield return false;
            }
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }

new SimpleStateMachine().Take(20).ToList().ForEach(x => Console.WriteLine(x));

C:\Program Files\Microsoft ASP.NET\ASP.NET Web Pages\v1.0\Assemblies\WebMatrix.Data.dll

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
 <add key="systemData:defaultProvider" value="System.Data.SqlClient" />
</appSettings>
<connectionStrings>
 <add name="Northwind"
     connectionString="Data Source=(local);Integrated Security = true;Initial Catalog=Northwind"
     providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>

using System;
using WebMatrix.Data;

namespace TestMicrosoftDataLibrary
{
 class Program
 {
     static void Main(string[] args)
     {
         getProducts();

         Console.Read();
         Console.WriteLine("Press a key ...");
     }

     private static void getProducts()
     {
         using (var db = Database.Open("Northwind"))
         {
             foreach (var product in db.Query("select * from products where UnitsInStock < @0", 20))
             {
                 Console.WriteLine(product.ProductName + " " + product.UnitsInStock);
             }
         }
     }
 }
}

private static void getCustomerFax()
{
         using (var db = Database.Open("Northwind"))
         {
             var product = db.Query("SELECT * FROM [Customers] WHERE City=@0", "Paris").FirstOrDefault();
             if (product != null)
                 Console.WriteLine(product.Fax);
             else
                 Console.WriteLine("not found.");
         }
}

private static void ExecQuery()
{
         using (var db = Database.Open("Northwind"))
         {
            int affectedRecords = db.Execute("UPDATE [Customers] SET fax = fax + '*' WHERE  City = @0", "Paris");
            Console.WriteLine("Affected records: {0}", affectedRecords);
         }
}

private static void ExecSPShowResult()
{
         using (var db = Database.Open("Northwind"))
         {
             var customer = db.Query("exec CustOrderHist @0", "ALFKI").FirstOrDefault();
             if (customer != null)
             {
                 Console.WriteLine(customer.ProductName);
             }
         }
}

private static void useFuncs()
{
         using (var db = Database.Open("Northwind"))
         {
             var query = db.Query("SELECT dbo.FN_GET_CATEGORY_TREE(@0) as Rec1", 3);
             foreach(var tree in query)
             {
                 Console.WriteLine(tree.Rec1);
             }
         }         
}