选择Linq不能将类型byte []隐式转换为System.web.httpPostedFileBase

Question

I am trying to do a linq select which join multiple table and 1 of the table consist of a byte data type.

My ViewModel is as per below:

public class ServiceRequestsViewModel
{
    public HttpPostedFileBase Attachment { get; set; }
}

My controller is as per below:

public IEnumerable<ServiceRequestsViewModel> ServiceRequestGetAll()
    {
        var result = (from srv in DB.Services
                      join srq in DB.ServiceRequests on srv.Id equals srq.ServiceId 
                      join srp in DB.ServiceApprovers on srq.ServiceId equals srp.ServiceId
                      select new ServiceRequestsViewModel
                      {
                          Id = srq.Id,
                          ServiceId = srq.ServiceId,
                          RequestorId = srq.RequestorId,
                          ApproverId = srp.UserId,
                          Name = srv.Name,
                          Description = srq.Description,
                          Status = srq.Status,
                          Attachment = srq.Attachment,
                          CreatedBy = srq.CreatedBy,
                          CreatedDate = srq.CreatedDate
                      })
                      ;
        return result.GroupBy(x => x.Id).Select(group => group.FirstOrDefault()).OrderByDescending(a => a.Status).ThenByDescending(b => b.CreatedDate);
    }

For the Attachment = srq.Attachment, I encounter the error: Cannot implicitly convert type byte[] to System.Web.HttpPostedFileBase.

Answer 1

HttpPostedFileBase is a wrapper class so you can access the data that your client uploaded with this call .

You are not in that scenario with your call.

Your data is already in your database. You need to pick a different datatype to return that data to your client. byte[] (that you already have) might be fine for your case, we cannot know, that's your job to decide.