Cannot implicitly convert type IQueryable to class

Question

I am trying to get multiple results into a list to send back to JS to populate a grid. The first query (_mappedQuery) is getting data. I then want to end up putting the values into the _udfList object. I keep getting variances on the error 'cannot convert queryable to class'

I have tried setting as lists, creating query objects, single class objects. All no luck so far

            MemberMNCFormsList _udfList = new MemberMNCFormsList();

            foreach (var _row in _udfTables) {
                System.Diagnostics.Debugger.Break();
                System.Diagnostics.Debugger.Launch();

                var _mappedQuery = (from res in Query<UdfColumnMapping>().AsNoTracking()
                                    join udf in Query<UserDefinedForms>().AsNoTracking() on res.Func_Area equals udf.Func_Area
                                    join ds in Query<Data_Set>().AsNoTracking() on res.Data_ID equals ds.DATA_ID
                                    join df in Query<DEFITEM>().AsNoTracking() on ds.DEF_ID equals df.DEF_ID
                                    where udf.UserDefinedForms_ID == _row.UserDefinedForms_ID &&
                                     (res.FieldName.ToLower().StartsWith("reviewname") ||
                                     res.FieldName.ToLower().StartsWith("disposition") ||
                                     res.FieldName.ToLower().StartsWith("reviewdate"))
                                    select (new MemberMNCForms {
                                        UserDefinedFormData_ID = _row.UserDefinedFormData_ID,
                                        FormId = udf.UserDefinedForms_ID,
                                        MappedColumnName = res.MappedColumnName,
                                        FieldName = res.FieldName,
                                        MappedTableName = res.MappedTableName,
                                        Reviewed_Name = _row.LAST_NAME.Trim() + ", " + _row.FIRST_NAME.Trim(),
                                        Reviewed_Date = _row.CreateDate.GetShortDateorEmpty().ToString()
                                    }));

                var _formRow = _mappedQuery.Select(t => new MemberMNCForms {
                    UserDefinedFormData_ID = t.UserDefinedFormData_ID,
                    FormId = t.FormId,
                    MappedColumnName = t.MappedColumnName,
                    FieldName = t.FieldName,
                    MappedTableName = t.MappedTableName,
                    Reviewed_Name = t.Reviewed_Name,
                    Reviewed_Date = t.Reviewed_Date
                })));

                _udfList.list.Add(_formRow);

   public sealed class MemberMNCForms {
        public Guid? UserDefinedFormData_ID { get; set; }
        public int FormId { get; set; }
        public string Reviewed_Name { get; set; }
        public string MappedColumnName { get; set; }
        public string FieldName { get; set; }
        public string MappedTableName { get; set; }
        public int? MNCDetermination_ID { get; set; }
        public string Reviewed_By { get; set; }
        public string Reviewed_Date { get; set; }
    }

    public sealed class MemberMNCFormsList : ErrorInfo
    {
        public List<MemberMNCForms> list = new List<MemberMNCForms>();
        public int Count { get; set; }
    }

I am trying to get the _udfList object populated with the values coming from _mappedQuery. The only thing I thought would work was to create a MemberMNCForms object for each record in _mappedQuery to then add to _udfList.list

Answer 1

_formRow is an IEnumerable<MemberMNCForms>

var _formRow = _mappedQuery.Select(t => new MemberMNCForms {
    UserDefinedFormData_ID = t.UserDefinedFormData_ID,
    FormId = t.FormId,
    MappedColumnName = t.MappedColumnName,
    FieldName = t.FieldName,
    MappedTableName = t.MappedTableName,
    Reviewed_Name = t.Reviewed_Name,
    Reviewed_Date = t.Reviewed_Date
})));

Here you are trying to add an IEnumerable<MemberMNCForms> to a List<MemberMNCForms>

_udfList.list.Add(_formRow);

You can't do this with .Add. You have to use .AddRange

Try this:

_udfList.list.AddRange(_formRow);

Answer 2

When you use linq like that, even if there is a single item in the list that you are Selecting on, it is just an expression tree until it is iterated on.

I assume that you are expecting a collection of MemberMNCForms back so you would need use AddRange instead of Add

_udfList.list.AddRange(_formRow);

To make sure that it has been executed, you can use ToList

_udfList.list.AddRange(_formRow.ToList());

If you are just expecting a single result, you can use SingleOrDefault.

var result = _formRow.SingleOrDefault();
if (result != null) {
    _udfList.list.Add(result);
}