How to make the position of a LINQ Query SELECT variable

Question

Is it possible to make the LINQ SELECT more flexible by not working with properties but with the column name? Maybe an example will help..I\'m trying to do the following (pseudo

Answer 1

Like I said in my comment (handles subproperties, like Type.Name, but not multiple fields) I let the fun to make the multi field version ;)

public static class DynamicLinkExtensions
{    
    public static IEnumerable<dynamic> Select<T>(this IQueryable<T> source, string memberAccess)
    {
        var propNames = memberAccess.Split('.');
        var type = typeof(T);
        var props = new List<PropertyInfo>();

        foreach (var propName in propNames)
        {
            var prop = type.GetProperty(propName);
            props.Add(prop);
            type = prop.PropertyType;
        }
        return source.Select(props.ToArray());
    }

    public static IEnumerable<dynamic> Select<T>(this IQueryable<T> source, PropertyInfo[] props)
    {
        var parameter = Expression.Parameter(typeof(T));
        var member = Expression.MakeMemberAccess(parameter, (MemberInfo)props.First());

        for (var i = 1; i < props.Length; i++)
        {
            member = Expression.MakeMemberAccess(member, (MemberInfo)props[i]);
        }

        Expression<Func<T, object>> expression = Expression.Lambda<Func<T, object>>(member, new[] { parameter });
        return source.Select(expression);
    }
}

Usage:

var names = DataContext.Customers.Select("Name").Cast<string>().ToList();

Answer 2

Maybe this will help you

from x In Entities
where ... select new {
  Value = x["Value"],
  Date = x["Date"],
  ID = x["ID"]
}