Question

Using ASP.NET MVC when I create my model, then a controller based on the model with CRUD operations, the CRUD views are generated. I added some code using Fluent API to require certain fields but for some reason the ModelState.IsValid passes even when these fields are not completed. What determines whether this passes or not? I thought it was based on your model property data types and other things like being required or maxlength, etc….

Also, I have manually added code to grab a list of Categories from the database and generate a checkbox for each one in the View. This is a navigation property for the Project model where there is a many-many relationship. To get the group of checked values in the Create(Project project) method in the controller I use:

var selected = Request["categories"].Split(',');

This however, throws the classic Object reference not set to an instance of an object error if no values are checked. So what I want to know is, how can I determine that this does not have any values so I can do something else once detected?

Answer 1

I added some code using Fluent API to require certain fields but for
some reason the ModelState.IsValid passes even when these fields are
not completed.

ASP.NET MVC doesn’t know anything about the Fluent API of Entity Framework and doesn’t evaluate this configuration. You only can use the data annotations which MVC will recognize:

[Required]
public string SomeProperty { get; set; }

---

…how can I determine that this does not have any values so I can do
something else once detected?

Not sure if I understand it correctly but I’d say:

var categories = Request["categories"];
if (categories != null)
{
    var selected = categories.Split(',');
    // ...
}
else
{
    // do something else
}