Entity Data Source error while processing report.

2 posts, 0 answers
  1. Mike
    Mike avatar
    7 posts
    Member since:
    Dec 2011

    Posted 22 Feb 2012 Link to this post

    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.
        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.
  2. Hrisi
    Hrisi avatar
    221 posts

    Posted 27 Feb 2012 Link to this post

    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,
    the Telerik team
    NEW in Q1'12: Telerik Report Designer (Beta) for ad-hoc report creation. Download as part of Telerik Reporting Q1 2012. For questions and feedback, use the new Telerik Report Designer Forum.
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