How to get bool value as returned object from the generics

Question

I have structure like this.

 public class ExportStructure
    {
        public string issueid { get; set; }
        public string filename {get;set;}
        public bool export { get; set; }
    }
public class ExportStructureManager
    {
        public List<ExportStructure> ExportIntoStructure { get; set; }
        public ExportStructureManager()
        {
            this.ExportIntoStructure = new List<ExportStructure>();
        }
        public ExportStructure AddToStructure(string issueid,string filename,bool exportornot)
        {
            ExportStructure expstr = new ExportStructure();
            expstr.issueid = issueid;
            expstr.filename = filename;
            expstr.export = exportornot;

            this.ExportIntoStructure.Add(expstr);
            return (expstr);
        }
        public bool GetStatusFromStructure(string issuekey)
        {
          return (from p in ExportIntoStructure
                where p.issueid == issuekey
                select p.export));
        }
    }

From the above one, I want to execute GetStatusFromStructure such that it should return me the export property status. For that one I written like that. But it is giving error as

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'bool'

at select p.export How to resolve this?

Answer 1

The problem is that your query is retrieve a sequence of bool values - one for each record matching your filter. Presumably you're only expecting a single result, so you could use Single:

return (from p in ExportIntoStructure
        // I assume you meant == rather than =
        where p.issueid == issuekey
        select p.export).Single();

But you should also consider what you want to happen if there are multiple results or none at all. The options are:

• Single
• SingleOrDefault
• First
• FirstOrDefault
• Last
• LastOrDefault

Which one is appropriate depends on what you want the behaviour to be in those situations.

You might also want to consider making this a non-query-expression:

return ExportIntoStructure.Where(p => p.issueid == issuekey)
                          .Select(p => p.export)
                          .Single();

Or even match to a single object first, then project:

return ExportIntoStructure.Single(p => p.issueid == issuekey)
                          .export;

Answer 2

Change statement

return (from p in ExportIntoStructure
            where p.issueid = issuekey
            select p.export));

to

return (from p in ExportIntoStructure
            where p.issueid == issuekey
            select p.export)).Single();

but be sure that issuekey is exists otherwise it will throw exception. or try its Default.

return (from p in ExportIntoStructure
            where p.issueid == issuekey
            select p.export)).SingleOrDefault();