>Also I'd suggest splitting the query so that (a) you can better identify where the error lies and (b) inspect the intermediate results:

tmp = matrixTemplateViewModel.TemplateValues.Where(x=>x.AtnameId!=matrixTemplate.PrimAxis);
>               
>matrixTemplateViewModel.ColumnAttributeId  = tmp.Select(x => new { x.AtnameId }).Distinct().FirstOrDefault();

In compile time I get 'Cannot implicitly convert type < anonymous type: int AtnameId to int > ' on the second line.