How do I use IValidatableObject?

Question

I understand that IValidatableObject is used to validate an object in a way that lets one compare properties against each other.

I\'d still like to have

Answer 1

The thing i don't like about iValidate is it seems to only run AFTER all other validation.
Additionally, at least in our site, it would run again during a save attempt. I would suggest you simply create a function and place all your validation code in that. Alternately for websites, you could have your "special" validation in the controller after the model is created. Example:

 public ActionResult Update([DataSourceRequest] DataSourceRequest request, [Bind(Exclude = "Terminal")] Driver driver)
    {

        if (db.Drivers.Where(m => m.IDNumber == driver.IDNumber && m.ID != driver.ID).Any())
        {
            ModelState.AddModelError("Update", string.Format("ID # '{0}' is already in use", driver.IDNumber));
        }
        if (db.Drivers.Where(d => d.CarrierID == driver.CarrierID
                                && d.FirstName.Equals(driver.FirstName, StringComparison.CurrentCultureIgnoreCase)
                                && d.LastName.Equals(driver.LastName, StringComparison.CurrentCultureIgnoreCase)
                                && (driver.ID == 0 || d.ID != driver.ID)).Any())
        {
            ModelState.AddModelError("Update", "Driver already exists for this carrier");
        }

        if (ModelState.IsValid)
        {
            try
            {