c# - Linq cast to list<T> -

i have following classes:

public class column {     public string name;     public string value; }  public class columnlist : list<column> {} 

then do:

var cols = (from c in othercolumnlist             select new column             {                name = c.name,             }).tolist() columnlist; 

however returns null. how can cast list?

what you're trying equivalent this:

animal animal = new animal(); dog dog = animal dog; 

one possible solution provide constructor takes existing list, , calls base constructor, such as:

public class columnlist : list<column> {     public columnlist(ienumerable<column> collection):          base(collection)     {     } } 

and build columnlist existing collection.

var collection = othercolumnlist.select(c => new column { name = c.name });  var columnlist = new columnlist(collection); 

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you provide extension method make easier:

public static class columnlistextensions {     public static tocolumnlist(this ienumerable<column> collection)     {         return new columnlist(collection);     }    }  var cols = othercolumnlist.select(c => new column { name = c.name })            .tocolumnlist();