Question

I have an MVP app that reads data from a SQL DB using EntityFramework. That data is copied from an external CMS website database, so the data isn’t always reliable.

One of the fields I read is of ‘bit’ datatype in SQL, and is either a 1 or 0, and ASP.NET MVC wants it as a boolean, otherwise I get errors about converting boolean to int.

The problem is sometimes that bit value can be NULL in the DB, and that crashes my MVC app. I can’t check for NULL, because I get errors that the boolean datatype can only be true or false.

Example

Model

namespace Foo.Models
{
    [Table("provider")]
    public class Bar
    {
        //can't check for null here, getter and setter only allow boolean
        public Boolean FooBar { get; set; }
    }
}

Controller

namespace Foo.Controllers
{
    public ActionResult BarList()
    {
         //Can't check for null here, because if(Boolean == null) will always evaluate to false
         List<Bar> bars = db.Bar.ToList();
         return View(bars);
    }
}

If FooBar is ever NULL, an error is thrown in the view that I can’t have a NULL in a boolean. How do I handle this situation?

Answer 1

You can use a generic Nullable<bool> (can also be expressed as bool?):

Nullable<bool> nullableBool;

Then use it as follows:

bool realBool = (nullableBool.HasValue && nullableBool);

// or

if (nullableBool == true) { ... } // true
else { ... } // false or null