linq相当于'select *'sql的泛型函数？

Question

I've got a generic<> function that takes a linq query ('items') and enumerates through it adding additional properties. How can I select all the properties of the original 'item' rather than the item itself (as the code below does)?

So equivalent to the sql: select *, 'bar' as Foo from items

foreach (var item in items)
{
    var newItem = new {
        item, // I'd like just the properties here, not the 'item' object!
        Foo = "bar"
    };

    newItems.Add(newItem);
}

Answer 1

There's no easy way of doing what you're suggesting, as all types in C# are strong-typed, even the anonymous ones like you're using. However it's not impossible to pull it off. To do it you would have to utilize reflection and emit your own assembly in memory, adding a new module and type that contains the specific properties you want. It's possible to obtain a list of properties from your anonymous item using:

foreach(PropertyInfo info in item.GetType().GetProperties())
    Console.WriteLine("{0} = {1}", info.Name, info.GetValue(item, null));

Answer 2

Shoot you wrote exactly what i was going to post. I was just getting some code ready :/

Its a little convoluted but anyways:

ClientCollection coll = new ClientCollection();
var results = coll.Select(c =>
{
    Dictionary<string, object> objlist = new Dictionary<string, object>();
    foreach (PropertyInfo pi in c.GetType().GetProperties())
    {
        objlist.Add(pi.Name, pi.GetValue(c, null));
    }
    return new { someproperty = 1, propertyValues = objlist };
});

Answer 3

from item in items
where someConditionOnItem
select
{
     propertyOne,
     propertyTwo
};

Answer 4

Ask the item to give them to you.

Reflection is one way... however, since all the properties are known at compile time, each item could have a method that helps this query get what it needs.

Here's some example method signatures:

public XElement ToXElement()
public IEnumerable ToPropertyEnumerable()
public Dictionary<string, object> ToNameValuePairs()

Answer 5

Suppose you have a collection of Department class:

   public int DepartmentId { get; set; }
   public string DepartmentName { get; set; }

Then use anonymous type like this:

        List<DepartMent> depList = new List<DepartMent>();
        depList.Add(new DepartMent { DepartmentId = 1, DepartmentName = "Finance" });
        depList.Add(new DepartMent { DepartmentId = 2, DepartmentName = "HR" });
        depList.Add(new DepartMent { DepartmentId = 3, DepartmentName = "IT" });
        depList.Add(new DepartMent { DepartmentId = 4, DepartmentName = "Admin" });
        var result = from b in depList
                     select new {Id=b.DepartmentId,Damartment=b.DepartmentName,Foo="bar" };