类型'System.Nullable`1 [System.Int32]'的表达式不能用于类型'System.Int32'\\ r \\ n的构造函数参数名称：arguments [0]

Question

I was doing the code below and EFCore throws

Expression of type System.Nullable'1[System.Int32] cannot be used for constructor parameter of type System.Int32'\\r\\nParameter name: arguments[0]

var data= await _dbContext.Set<Person>().Select(person =>person.Profile != null ? 
new ProfileDto(org.Profile.Id , org.Profile.Nickname) : null).ToListAsync();

A Person either have a profile or none, so Profile property on Person is optional.

Answer 1

Another work around is to create a static method on ProfileDto, for example,

public class ProfileDto
{
  public static ProfileDto CreateFromDb(int id, string nickname)
  {
    // this is a constuctor.
     return new ProfileDto(id,nickname);
  }
}

//Then do:

{
var data= await _dbContext.Set<Person>().Select(person =>person.Profile != null ? 
ProfileDto.CreateFromDb(org.Profile.Id , org.Profile.Nickname) : null).ToListAsync();
}