c# - Strongly Typed Generic Attribute alternatives -

lets start simple view model:

public class myviewmodel {   public string value { get; set; }   public ienumerable<selectlistitem> values { get; set; } } 

a drop down list might like:

@html.dropdownlistfor(m => m.value, model.values) 

however, because drop down list requires 2 values can't used like:

public class myviewmodel {   [uihint("dropdownlist")]   public string value { get; set; }   public ienumerable<selectlistitem> values { get; set; } } 

with view containing:

@html.editformodel() 

because there no inherent way drop down know source, until derrive uihint:

public dropdownlistattribute : uihintattribute {   public dropdownlistattribute (string valuessource)     : base("dropdownlist", "mvc")   {   } } 

then 1 might use like:

public class myviewmodel {   [dropdownlist("planets")]   public string planetid{ get; set; }   public ienumerable<selectlistitem> planets { get; set; }    [dropdownlist("cars")]   public string carid{ get; set; }   public ienumerable<selectlistitem> cars { get; set; } } 

however, isn't typed, renames 1 of magic strings or propery names without changing other , breaks @ run-time.

one theoretical solution create generic attribute:

public dropdownlistattribute<tmodel, tvalue> : uihintattribute {   public dropdownlistattribute (expression<func<tmodel, tvalue> expression)     : base("dropdownlist", "mvc")   {   } } 

and usage be:

public class myviewmodel {   [dropdownlist<myviewmodel, ienumerable<selectlistitem>>( m => m.planets)]   public string planetid{ get; set; }   public ienumerable<selectlistitem> planets { get; set; } } 

but (currently) generic attributes aren't allowed :/

another option encapsulate 2 single class modelbinder can recreate on post-back:

public class dropdownlisttemplate {   public string selectedvalue { get; set; }   public ienumerable<selectlistitem> values { get; set; } }  public class myviewmodel {   public dropdownlisttemplate planet { get; set; } } 

this creates simplicity in viewmodel, binding , editfor/displayfor templates limited knowledge of automapper adds complexity when automapper mapping properties of class properties. far know can't simply:

public class myplanets {   public string selectedplanet { get; set; } }  mapper.createmap<myplanets, myviewmodel>(); mapper.createmap<myviewmodel, myplanets>(); 

is there easier way automapper map these values auto-magically or there way create strongly-typed non-generic attribute?

you name property in planets "planetselectedvalue" cause automapper automagically determine value goes there. (i.e. planet.selectedvalue maps planetselectedvalue)

this similar magic string problem in if change property name, automapper no longer know put value, no different other automapper issue.

public class myplanets {     public string planetselectedvalue { get; set; } } 

or:

use automapper's ignoremap attribute ignore dropdownlisttemplate property , make separate automapper-friendly planetid property manipulates values inside dropdownlisttemplate.

public class dropdownlisttemplate {     public string selectedvalue { get; set; }     public ienumerable<selectlistitem> values { get; set; } }  public class myviewmodel {     [ignoremap]     public dropdownlisttemplate planet { get; set; }     public string planetid     {         { return planet.selectedvalue; }         set { planet.selectedvalue = value; }     } } 

also, when possible project, @ c# 6.0 nameof() expression pull in name of property without using magic string.