Question

i have this query in my code I am getting this Error.

 var auditMandate = (from ae in genDB.AuditEvent
                     join at in genDB.AuditTable on // snip
                     select ae)
                     .OrderByDescending(x => 
                         x.DateTime_Updated).Take(500)
                     .Distinct().ToList();

An error occurred while executing the command definition. See the inner exception for details.
The xml data type cannot be selected as DISTINCT because it is not comparable. The xml data type cannot be selected as DISTINCT because it is not comparable.

is that something I am doing wrong this Linq?

Thanks

Answer 1

This is doable. Take the query you have but get rid of the Distinct call. You still want a concrete list however so keep ToList(). Then follow this idea (since I don’t know your xml structure):

My Table

CREATE TABLE [dbo].[XmlTable](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [data] [xml] NULL
)

My Data

insert into XmlTable
values('<list id=''a''><items></items></list>')
insert into XmlTable
values('<list id=''b''><items></items></list>')
insert into XmlTable
values('<list id=''a''><items></items></list>')

My Comparer

    public class MyXDocumentCoparer : IEqualityComparer<XDocument>
    {
        public bool Equals(XDocument x, XDocument y)
        {
            var xId = x.Root.Attribute("id").Value;
            var yId = y.Root.Attribute("id").Value;
            return xId == yId;
        }

        public int GetHashCode(XDocument obj)
        {
            var id = obj.Root.Attribute("id").Value;
            return id.GetHashCode();
        }
    }

My Code

    using (var ctx = new xmltestEntities())
    {
        // this would be your concrete list
        var rawData = ctx.XmlTables.ToArray();

        var processedData = rawData
            .Select(row => XDocument.Parse(row.data))
            .Distinct(new MyXDocumentCoparer());

        // you'll only get two, boom!
        foreach (var item in processedData)
            Console.WriteLine(item.Root.Attribute("id"));

        Console.ReadLine();
    }