How to select * and calculate field in Entity Framework?-CodePudding

I want to select all pictures and calculate IsAnnotated field, but how I can select * fields and apply this IsAnnotated field? Because in this example for now only selected IsAnnotated. Do we have a possibility to prevent manually write something like Id = picture.Id, title = picture.Title?

var picture = await _dbContext.Pictures
                .Select(picture => new Picture
                {
                    IsAnnotated = _dbContext.Annotations.Any(x => x.PictureId == picture.Id),
                })
                .Where(s => ids.Contains(s.Id))
                .ToListAsync();

CodePudding user response：

First, select the Pictures you want by ids list:

 var pictures = _dbContext.Pictures
            .Where(s => ids.Contains(s.Id));

Second, calculate the IsAnnotated field with foreach - this is not a case of 'select', this is an update case. (Convert to 'List' for using the ForEach linq function, you can use the foreach statement instead):

pictures.ToList().ForEach(a => a.IsAnnotated = _dbContext.Annotations.Any(x => x.PictureId == a.Id));

CodePudding user response：

You can do something like this.

    Var pictures = _dbcontext.Pictures.Where(x=> IDs.Contains(x.id));

var annotations = await pictures.Join(_dbContext.annotation, pic => pic.id, ann => ann.pictureId, (pic, ann) => new 
    {
       Annotation = ann.IsAnnotated
    }.ToListAsync();

Or instead an anonymous type you can pass a model if you want.

Sorry if it's not readable but I wrote it from my phone!!