title: Error message Nullable object must have a value
body: <p>I have a null error on my DTO object at runtime:</p>
  
  <p><img src="https://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>