Entity Data Source error while processing report.

[Mike]

I get an error(in the designer preview) that reads "An error has occured while processing Report 'MyReport': Unable to cast the type 'System.Nullable '1' to type 'System.Object'. LINQ to Entities only supports casting Entity Data Model primitive types."

I know that this has to do with the datasource I'm choosing to use. I'm 'extending' the model's Entity partial class with a method that should return an enumerable collection of classes that contain my data that I pulled from the model with LINQ. Sort of like the code that is given here: http://www.telerik.com/ClientsFiles/311739_EntityFrameworkDemo.zip

Here's the method I'm using to get data:

public partial class MyDataModelEntities
    {
        public IEnumerable<SessioinReportData> QuerySessionReport()
        {
            var query = from user in this.users
                        from session in this.sessions
                        where user.id.Equals(session.assigned_user_id)
                        select new SessioinReportData
                        {
                            CreatedBy = user.user_name ?? "",
                            SessionType = session.session_type ?? "Unknown",
                            DateEntered = (session.date_entered != null ? session.date_entered.Value.ToString("MM/dd/yyyy") : "n/a"),
                            NumericID = session.numeric_id,
                            Status = session.status
                        };
            return query;
        }

    }

    /// <summary>
    /// This contains data needed for the report
    /// </summary>
    public class SessioinReportData
    {
        public string CreatedBy { get; set; }
        public string SessionType { get; set; }
        public string DateEntered { get; set; }
        public int NumericID { get; set; }
        public string Status { get; set; }

    }

Here's the code for one of the entity objects that I'm using:

namespace MyProject.Web.Model
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.ComponentModel.DataAnnotations;
    using System.Linq;
    using System.ServiceModel.DomainServices.Hosting;
    using System.ServiceModel.DomainServices.Server;

    // The MetadataTypeAttribute identifies sessionMetadata as the class
    // that carries additional metadata for the session class.
    [MetadataTypeAttribute(typeof(session.sessionMetadata))]
    public partial class session
    {
        internal sealed class sessionMetadata
        {

            // Metadata classes are not meant to be instantiated.
            private sessionMetadata()
            {
            }

            public Nullable<Guid> assigned_user_id { get; set; }

            public Nullable<bool> confirm_flag { get; set; }

            public Nullable<Guid> created_by { get; set; }

            public Nullable<DateTime> date_end { get; set; }

            public Nullable<DateTime> date_entered { get; set; }

            public Nullable<DateTime> date_modified { get; set; }

            public Nullable<DateTime> date_start { get; set; }

            public Guid id { get; set; }

            public Nullable<Guid> modified_user_id { get; set; }

            public string notes { get; set; }

            public Nullable<Guid> parent_id { get; set; }

            public string session_type { get; set; }

            public string status { get; set; }
        }
    }
}

I've tried adjusting for the Nullable types in a dew different ways. Nothing seems to work. If you don't know of any suggestions on how to fix this, at least tell me what you think the problem lies with.

[Hrisi]

Hello Mike,

One way to discover what is going wrong is to use QuerySessionReport method in the test. I guess you have not tested this method with your actual data. Because we do not know your data we cannot guess/test your methods, there is a possibility the problem is hidden in your LINQ query.

A similar problem is described here, where you can find a possible solution.

All the best,
Hrisi
the Telerik team