How do you implement the equivalent of SQL IN() using .net

Question

In .net (c# or vb) expressions, how would you implement SQL\'s handy IN() functionality?

i.e. value in (1, 2, 4, 7)

rather than:

value = 1 or value =

Answer 1

Here's some simple Linq with some pseudo code. No need to re-invent the wheel.

int[] values = new int[]{1, 2, 4, 7};
int target = 2;
bool contains = values.Any(v => v == target);

Or use .Contains as some have suggested.

Answer 2

I know there are LOADS of answers here, but here's my take on the subject, used daily in SubSonic. it's an extension method:

public static IQueryable<T> WhereIn<T, TValue>(
                this IQueryable<T> query,
                Expression<Func<T, TValue>> selector, 
                params TValue[] collection) where T : class
{
    if (selector == null) throw new ArgumentNullException("selector");
    if (collection == null) throw new ArgumentNullException("collection");
    ParameterExpression p = selector.Parameters.Single();

    if (!collection.Any()) return query;

    IEnumerable<Expression> equals = collection.Select(value =>
       (Expression)Expression.Equal(selector.Body,
            Expression.Constant(value, typeof(TValue))));

    Expression body = equals.Aggregate(Expression.Or);
    return query.Where(Expression.Lambda<Func<T, bool>>(body, p));
}

and WhereNotIn:

public static IQueryable<T> WhereNotIn<T, TValue>(
                this IQueryable<T> query, 
                Expression<Func<T, TValue>> selector, 
                params TValue[] collection) where T : class
{
    if (selector == null) throw new ArgumentNullException("selector");
    if (collection == null) throw new ArgumentNullException("collection");
    ParameterExpression p = selector.Parameters.Single();

    if (!collection.Any()) return query;

    IEnumerable<Expression> equals = collection.Select(value =>
       (Expression)Expression.NotEqual(selector.Body,
            Expression.Constant(value, typeof(TValue))));

    Expression body = equals.Aggregate(Expression.And);

    return query.Where(Expression.Lambda<Func<T, bool>>(body, p));
}

usage:

var args = new [] { 1, 2, 3 };
var bookings = _repository.Find(r => r.id > 0).WhereIn(x => x.BookingTypeID, args);
// OR we could just as easily plug args in as 1,2,3 as it's defined as params
var bookings2 = _repository.Find(r => r.id > 0).WhereIn(x => x.BookingTypeID, 1,2,3,90);

var bookings3 = _repository.Find(r => r.id > 0).WhereNotIn(x => x.BookingTypeID, 20,30,60);

this really makes me smile every time i review it :)

jim

[edit] - originally sourced from here on SO but modified to use iqueryable and params: 'Contains()' workaround using Linq to Entities?

Answer 3

You can use Contains() method on the list.

    int myValue = 1;
    List<int> checkValues = new List<int> { 1, 2, 3 };

    if (checkValues.Contains(myValue))
        // Do something