asp.net mvc 4 - MVC RequiredIf Attribute - IsValid value parameter always null -

i implementing requiredif validation attribute , value being passed isvalid method null.

requiredifattribute class

    public class requiredifattribute : validationattribute {     private requiredattribute innerattribute = new requiredattribute();     public string dependentproperty { get; set; }     public object targetvalue { get; set; }      public requiredifattribute(string dependentproperty, object targetvalue)     {         this.dependentproperty = dependentproperty;         this.targetvalue = targetvalue;     }      public override bool isvalid(object value)     {         return innerattribute.isvalid(value);     } } 

viewmodel

        [required]     [display(name = "are student?")]     public bool? isstudent { get; set; }      [requiredif("isstudent", true, errormessage = "you must upload photo of student id if wish register student.")]     [display(name = "student id")]     [fileextensions("jpg|jpeg|png|pdf", errormessage = "file not in correct format.")]     [maxfilesize(2 * 1024 * 1024, errormessage = "you may not upload files larger 2 mb.")]     public httppostedfilebase studentid { get; set; } 

editortemplate

    @model bool? @using system.web.mvc; @{     var options = new list<selectlistitem>     {         new selectlistitem { text = "yes", value = "true", selected =  model.hasvalue && model.value },         new selectlistitem { text = "no", value = "false", selected =  model.hasvalue && model.value }     };      string defaultoption = null;      if (viewdata.modelmetadata.isnullablevaluetype)     {         defaultoption = "(select)";     } }  @html.dropdownlistfor(m => m, options, defaultoption) 

every time form submitted, requiredif error message thrown , have feeling has null value described initially. doing wrong? thanks!

note: html appears rendering properly, don't think that's problem.

    <select data-val="true" data-val-required="the student? field required." id="isstudent" name="isstudent"><option value="">(select)</option> <option value="true">yes</option> <option value="false">no</option> </select> 

because code -

public class requiredifattribute : validationattribute {     private requiredattribute innerattribute = new requiredattribute();     public string dependentproperty { get; set; }     public object targetvalue { get; set; }      public requiredifattribute(string dependentproperty, object targetvalue)     {         this.dependentproperty = dependentproperty;         this.targetvalue = targetvalue;     }      public override bool isvalid(object value)     {         return innerattribute.isvalid(value);     } } 

you using requriedatrribute. simulate behaves life requiredif have implement logic check whether target property value true or false. not doing , returning innerattribute. mere required not requiredif -

public override bool isvalid(object value) {     return innerattribute.isvalid(value); } 

modify function checking -

public override bool isvalid(object value) {     //if referred property true         return innerattribute.isvalid(value);     //else     return true }