'DataSet does not support System.Nullable.' Error filling out report with Datetime Null data

I am filling out a report in crystal report with a class that has null data types in c # when I try to fill out the report I get the following error:

  

'DataSet does not support System.Nullable < & gt ;.' crystal report.

 public class SterelizationProcess
    {
        [Key]
        public int SterelizationID { get; set; }
        [ForeignKey("Handling")]
        public String HandlingUnit { get; set; }
        public virtual HandlingUnits Handling { get; set; }

        public int StatusID { get; set; }
        public virtual StatusHandlingUnit St { get; set; }

        [Required]
        public DateTime? DateReceived { get; set; }
        public DateTime? Start_the_Sterilization_Process_Date { get; set; }
        public DateTime? Complete_the_Sterilization_Process_Date { get; set; }
}