validation - Conditionally require all fields in class depending on property -

i have address class, used 2 properties - mailingaddress , streetaddress.

how can make streetaddress required , mailingaddress not?

    public address mailingaddress { get; set; }      [required(errormessage = "address, city, state, , zip code required.")]     public address streetaddress { get; set; }    public class address     {         [displayname("address")]         public string streetaddress { get; set; }         [displayname("city")]         public string city { get; set; }         [displayname("state")]              public string selectedstate { get; set; }         [datatype(datatype.postalcode)]         [regularexpression(@"^\d{5}$|^\d{5}-\d{4}$", errormessage="the postal code should in format 00000 or 00000-0000")]         [displayname("zip")]         public string zip { get; set; }     } 

i treat them little differently. propose have 2 different address models , put them single viewmodel.

let's take address class , give virtual keywords can override class properties.

public class address {     [displayname("address")]     public virtual string streetaddress { get; set; }     [displayname("city")]     public virtual string city { get; set; }     [displayname("state")]          public virtual string selectedstate { get; set; }     [datatype(datatype.postalcode)]     [regularexpression(@"^\d{5}$|^\d{5}-\d{4}$", errormessage="the postal code should in format 00000 or 00000-0000")]     [displayname("zip")]     public virtual string zip { get; set; } } 

now let's create new model inherits our address class.

public class mandatoryaddress : address {     [required]     public override string streetaddress { get; set; }     [required]     public override string city { get; set; }     [required]     public override string selectedstate { get; set; }     [required]     public override string zip { get; set; } } 

now let's create our viewmodel

public class myformviewmodel {     public mandatoryaddress streetaddress { get; set; }     public address mailingaddress { get; set; } } 

a view might this

@{     viewbag.title = "my sample form"; }  @model testapp.models.myformviewmodel  <h2>@viewbag.title</h2>  @using (html.beginform()) {     <fieldset>         <legend>street address</legend>         <div>             @html.labelfor(x => x.streetaddress.streetaddress)             @html.editorfor(x => x.streetaddress.streetaddress)             @html.validationmessagefor(x => x.streetaddress.streetaddress)         </div>         <div>             @html.labelfor(x => x.streetaddress.city)             @html.editorfor(x => x.streetaddress.city)             @html.validationmessagefor(x => x.streetaddress.city)         </div>         <div>             @html.labelfor(x => x.streetaddress.selectedstate)             @html.editorfor(x => x.streetaddress.selectedstate)             @html.validationmessagefor(x => x.streetaddress.selectedstate)         </div>         <div>             @html.labelfor(x => x.streetaddress.zip)             @html.editorfor(x => x.streetaddress.zip)             @html.validationmessagefor(x => x.streetaddress.zip)         </div>     </fieldset>     <fieldset>         <legend>mailing address</legend>         <div>             @html.labelfor(x => x.mailingaddress.streetaddress)             @html.editorfor(x => x.mailingaddress.streetaddress)             @html.validationmessagefor(x => x.mailingaddress.streetaddress)         </div>         <div>             @html.labelfor(x => x.mailingaddress.city)             @html.editorfor(x => x.mailingaddress.city)             @html.validationmessagefor(x => x.mailingaddress.city)         </div>         <div>             @html.labelfor(x => x.mailingaddress.selectedstate)             @html.editorfor(x => x.mailingaddress.selectedstate)             @html.validationmessagefor(x => x.mailingaddress.selectedstate)         </div>         <div>             @html.labelfor(x => x.mailingaddress.zip)             @html.editorfor(x => x.mailingaddress.zip)             @html.validationmessagefor(x => x.mailingaddress.zip)         </div>     </fieldset>      <div>         <input type="submit" />     </div> } 

a controller might this:

public class formcontroller : controller {     //     // get: /form/      [httpget]     public actionresult index()     {         myformviewmodel viewmodel = new myformviewmodel();         return view(viewmodel);     }      [httppost]     public actionresult index(myformviewmodel viewmodel)     {         return view(viewmodel);     }  } 

bonus experience points:

an alternative way (more complex arguably 'better') create own custom [required] attribute can apply class (i.e. streetaddress). attribute have go through each property of class , apply [required] attribute.