ModelState is invalid for a nullable property

Question

I have a model where the property CompanyID allows a null value

public partial class ReportTemplateItem
{
    [Key]
    public int ReportTemplateItemID { get; set; }

    [Required]
    public int ReportTemplateID { get; set; }
    
    public int? CompanyID { get; set; }
}

In the DBContext OnModelCreating, there is no property declared for CompanyID

But when posting the ModelState is Invalid. The form works as intended if I remove ModelState validation

ModelState Invalid

Accepting a null value appears to be the default behavior for Model Validation, what am i missing?

Razor Pages with EF Core 3.0, Nullable Reference Types is disabled

many thanks

edit - the invalid object at time of validation

Answer 1

If this is any help, you may try just not to send a null value at all (exclude it from data being sent).

For example, instead of sending the folowing json data:

    var data = {
        reportTemplateItemID: 1,
        reportTemplateID: 2,
        companyID: null
    };

send only:

    var data = {
        reportTemplateItemID: 1,
        reportTemplateID: 2
    };

If you have a complex object, you may easily strip all nulls before making an ajax call:

// let's remove null and undefined values
// an easy way is to serialize using a replacer function and deserialize back
const str = JSON.stringify(data, function(key, value) { return value === null ? undefined : value; });
const newData = JSON.parse(str);

See how it works:

var data = { "aaa" : undefined, "bbb": null, ccc : ""}
// newData = "{"ccc":""}"

ModelState validation won't fail in such case (as long as the value type is nullable), at least in ASP.NET Core 3.1 (I didn't check other versions).