C# Generate Expression to Select with Where

whereequal.cs

private IQueryable<T> WhereEqual<T>(IQueryable query, string prop, object param)
{
    var select = Expression.Parameter(typeof(T), "select");

    MemberExpression property = null;
    foreach (var node in prop.Split('.'))
    {
        property = property == null 
            ? Expression.Property(select, node)
            : Expression.Property(property, node);
    }

    var expression = Expression.Equal(property, Expression.Constant(param));

    var where = Expression.Call(
        typeof(Queryable),
        "Where",
        new[] { query.ElementType },
        query.Expression,
        Expression.Lambda<Func<T, bool>>(expression, select));

    return query.Provider.CreateQuery<T>(where);
}

/* Usage:
*
*  var query = from customer in customers select new Wrapper { Customer = customer };
*  query = WhereEqual<Wrapper>(query, "Customer.Id", id);
*/