MVC ViewModel Custom Property not populating if null exists - asp.net

Question

I have a very simple viewmodel, based on a Customer domain model.
I'm adding one property to it: CustomerNameAddress which is made up of the CustomerName, Contact and Town of the domain model.
However, if any of CustomerName, Contact or Town are null - then CustomerNameAddress is also null.
Is there anyway of checking for null within my query below, and changing it to "", so that my viewmodel works correctly?
I had tried:
CustomerNameAddress = (p.CustomerName || "") + ", " + (p.Contact || "") + ", " + (p.Town || "")
... but VS advised Operator '||' cannot be applied to operands of type 'string' and 'string'
My controller code is below.
Thank you,
Mark
public JsonResult Lookup(string id)
{
string userName = null;
if (HttpContext.User.Identity.IsAuthenticated)
{
userName = HttpContext.User.Identity.Name;
}
var customers = from p in db.Customers
where p.UserName.Equals(userName)
select new CustomerLookupViewModel
{
CustomerId = p.CustomerId,
Email = p.Email,
CustomerNameAddress = p.CustomerName + ", " + p.Contact + ", " + p.Town
};
return Json(customers, JsonRequestBehavior.AllowGet);
}
UPDATE
I amended the code to:
But now get the error on p.Contact (underlined above) advising: Cannot implicitly convert type 'string' to 'bool'
However, my viewmodel clearly has Contact as a string:
public class CustomerLookupViewModel
{
public string CustomerNameAddress { get; set; }
public int CustomerId { get; set; }
[Required]
[Display(Name = "Customer Name")]
public string CustomerName { get; set; }
[Display(Name = "Customer Contact")]
public string Contact { get; set; }
2nd Update - now working
I updated the conditions to be enclosed in brackets, and it's now working:
CustomerNameAddress = ((p.CustomerName == null) ? "" : (p.CustomerName + ", ")) +
((p.Contact == null) ? "" : (p.Contact + ", ")) +
((p.Town == null) ? "" : (p.Town))

Answer 1

You can use condition operator ? :
CustomerNameAddress = (p.CustomerName == null || p.Contact == null || p.Town == null ) ? "" : p.CustomerName + ", " + p.Contact + ", " + p.Town
Query would be.
var customers = from p in db.Customers
where p.UserName.Equals(userName)
select new CustomerLookupViewModel
{
CustomerId = p.CustomerId,
Email = p.Email,
CustomerNameAddress = (p.CustomerName == null || p.Contact == null || p.Town == null ) ? "" : p.CustomerName + ", " + p.Contact + ", " + p.Town
};

Answer 2

Is there anyway of checking for null within my query below, and
changing it to "", so that my viewmodel works correctly?
something like this should do the trick
CustomerNameAddress =
(string.IsNullOrWhiteSpace(p.CustomerName) ? "" : (p.CustomerName + ", ")) +
(string.IsNullOrWhiteSpace(p.Contact) ? "" : (p.Contact + ", ")) +
(string.IsNullOrWhiteSpace(p.Town) ? "" : (p.Town + ", "))
You might want to create a procedure for that so you can reuse that simple logic.