c# - entity framework validation context - null exception in null test -

i working on pc configurator application , have problem validating. point of app check if socket on motherboard same socket of cpu etc.

i made code first database using scaffolding in visual studio 2013.

public class configuration : ivalidatableobject {     [key]     public int configurationid { get; set; }      [required]     [stringlength(50, minimumlength = 3)]     [displayname("configuration name")]     public string configname { get; set; }      [foreignkey("mb_id")]     public motherboard motherboard { get; set; }      [column("mb_id", typename = "int")]     public nullable<int> mb_id { get; set; }      [foreignkey("cpu_id")]     public cpu cpu { get; set; }      [column("cpu_id", typename = "int")]     public nullable<int> cpu_id { get; set; } } 

this part of configuration model using (rest of looks pretty similar - other components)

i scaffolded model controller.

this start of validation , seems problem somewhere here (at least vs says so).

public ienumerable<validationresult> validate(validationcontext validationcontext) {     if (motherboard == null) { throw new argumentnullexception("motherboard"); }     if (cpu == null) { throw new argumentnullexception("cpu"); }     if (gpu == null) { throw new argumentnullexception("gpu"); }     if (hdd == null) { throw new argumentnullexception("hdd"); }     if (ram == null) { throw new argumentnullexception("ram"); }     if (power == null) { throw new argumentnullexception("power"); }     if (case == null) { throw new argumentnullexception("case"); }      if (motherboard.cpu.toupper().trim() != cpu.socket.toupper().trim())     {             yield return new validationresult("cpu socket not match.", new[] { "cpu_id" });     } } 

when create pc configuration without validation, goes database. when try validation says cpu (in null test) null , throws null exception. screenshot vs.

it never throws on motherboard on next item (on second item).

cpu seems treated entity framework navigation property. without more information suggests you'll need to:

1. using system.data.entity in whatever unit selects model
2. .include(c => c.cpu) before enumerating query database

if that's navigation property, appears, may lazily loaded documented in entity framework materials.

this means though values seem exist in database actual collection --or in case, reference-- null in memory. tell entity framework "include" items when fetch:

var configuration = db.configurationsorsomething     .include(c => c.cpu)     .where(c => c.deletedorwhatever == false)     .tolist();  var cpu = configuration.cpu;  if(cpu == null)     debug.writeline("something else problem. :("); 

you did you've seen value in database. can't see code you've used select entity database --or else, if there else. can see cpu type you've defined , referenced. model looks ef code first / table-per-type if need know more along tutortial.

note: i've re-read comments in new light. when asked if getting database agreed "created normally" without validation.

i'm considering entire setup simple validation failure. if validation says cpu null... cpu null.

so: code using create new instance of configuration entity? not assigning value cpu?