Error message Nullable object must have a value
<p>I have a null error on my DTO object at runtime:</p>

<p><img src="http://i.stack.imgur.com/XSsbH.png" alt="enter image description here"></p>

<p>I didn't understand because column is nullable: </p>

<pre><code>[DataContract]
public class SearchParametersCompanyDTO
{
    public SearchParametersCompanyDTO();

    [DataMember]
    public CompanyColumnsEnumDTO? Column { get; set; }
    [DataMember]
    public int PageIndex { get; set; }
    [DataMember]
    public int PageSize { get; set; }
    [DataMember]
    public string Term { get; set; }
}

[DataContract]
public enum CompanyColumnsEnumDTO
{
    [EnumMember]
    CompanyName = 0,
    [EnumMember]
    City = 1,
    [EnumMember]
    PostCode = 2,
}
</code></pre>

<p>It must be a conversion problem because null is accepted on Column:</p>

<pre><code>        var dto = new SearchParametersCompanyDTO
        {
            PageIndex = pageIndex,
            PageSize = defaultPageSize,
            Term = term,
            Column = null
        };
</code></pre>

<p>Any idea?</p>
