c# - Cannot Convert Item to its interface exception -

i have following class , interface:

public interface ifieldfiller     {         string content { get; set; }         boolean nullable { get; set; }         string name { get; set; }     } 

and

[datacontract] public class fieldfiller : ifieldfiller {     [datamember]     public string content { get; set; }      [datamember]     public boolean nullable { get; set; }      [datamember]     public string name { get; set; }      [datamember]     public storedprocedure storedprocedure { get; set; }      [datamember]     public string namespace { get; set; } } 

i use following linq statement build list of these objects:

fields =  temp.merged_fields.select(f => new fieldfiller { name = f.name, namespace = f.@namespace, storedprocedure = new storedprocedure { name = f.sproc1.name, parameters = f.field_params.todictionary(p => p.sprocparam.name, p=>p.value)}}).tolist() 

and keep getting following exception:

error   1   cannot implicitly convert type 'system.collections.generic.list<services.data.emailtemplateaccess.contracts.fieldfiller>' 'system.collections.generic.list<services.data.emailtemplateaccess.contracts.ifieldfiller>'     

i don't understand why getting error when fieldfiller implements ifieldfiller. have verified in correct namespaces. appreciated.

fieldfiller ifieldfiller list<fieldfiller> not list<ifieldfiller>, can cast accordingly:

fields =  temp.merged_fields     .select(f => (ifieldfiller)new fieldfiller { name = f.name, namespace = f.@namespace, storedprocedure = new storedprocedure { name = f.sproc1.name, parameters = f.field_params.todictionary(p => p.sprocparam.name, p=>p.value)}})     .tolist() 

or, .net 4 can use this(see: covariance , contravariance):

...     .select(f => new fieldfiller { ... })     .tolist<ifieldfiller>(); 

why it's not safe:

• https://stackoverflow.com/a/4038168/284240 and
• https://stackoverflow.com/a/8925442/284240