Sometimes you need to get a result set for a field that contains any value from an array.
The default approach in LINQ would be:

from var c in data where array.Contains(c.field) select c;

which creates a T-SQL that looks like that:

select * from data where data.field in (1,2,3,...)

Unfortunately, this would produce an error with EF, since Contains is currently not implemented with .NET 3.5SP1.

Therefore, we need a workarround that builds an expression that implements an or for each indiviudal value in the array to be compared against the field:

private void button2_Click(object sender, RoutedEventArgs e)
{
    int[] types = new int[] { 1, 2, 3, 10 };
    using (TomsPortal.TomsPortalEntities1 tp = new TomsPortalEntities1())
    {
        var r = from node in tp.Node where node.Taxonomy.Id != 3 where Contains<Node, int>(types) select node;
        r = r.Where(Contains<Node, int>(node => node.Id, types));

        foreach (var o in r)
        {
            Trace.WriteLine(o.Id);
        }
    }
}

static Expression<Func<TElement, bool>> Contains<TElement, TValue>(this Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
{
    if (null == valueSelector) { throw new ArgumentNullException("valueSelector"); }
    if (null == values) { throw new ArgumentNullException("values"); }
    if (!values.Any()) return e => false;

    var equals = from value in values
        select
            System.Linq.Expressions.Expression.Equal(
                valueSelector.Body,
                System.Linq.Expressions.Expression.Constant(value, typeof(TValue))
            );

    var body = equals.Aggregate((accumulate, equal) =>
        System.Linq.Expressions.Expression.Or(accumulate, equal));

    ParameterExpression p = valueSelector.Parameters.Single();
    var ex = System.Linq.Expressions.Expression.Lambda<Func<TElement, bool>>(body, p);
   
    return ex;
}