重构项目结构，移除Assignment相关功能，优化Submission模块

Entities/Contracts/Exam.cs

@@ -0,0 +1,122 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations.Schema;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Entities.DTO;
+
+namespace Entities.Contracts
+{
+	[Table("exams")]
+	public class Exam
+	{
+		[Key]
+		[Column("id")]
+		public Guid Id { get; set; }
+
+		[Required]
+		[Column("title")]
+		[StringLength(255)]
+		public string Title { get; set; }
+
+		[Column("description")]
+		public string Description { get; set; }
+
+		[Column("subject_id")]
+		public Guid SubjectId { get; set; }
+		[ForeignKey(nameof(SubjectId))]
+		public virtual Subject Subject { get; set; }
+
+		[Required]
+		[Column("exam_struct_id")]
+		[ForeignKey(nameof(ExamStruct))]
+		public Guid ExamStructId { get; set; }
+		public virtual ExamQuestion ExamStruct { get; set; }
+
+		[Column("exam_type_id")]
+		public Guid ExamTypeId { get; set; }
+		[ForeignKey(nameof(ExamTypeId))]
+		public virtual ExamType ExamType { get; set; }
+
+		[Column("created_by")]
+		public Guid CreatorId { get; set; }
+		[ForeignKey(nameof(CreatorId))]
+		public virtual User Creator { get; set; }
+
+		[Required]
+		[Column("due_date")]
+		public DateTime DueDate { get; set; }
+
+		[Column("total_points")]
+		public byte TotalQuestions { get; set; }
+
+		[Column("score")]
+		public float Score { get; set; }
+
+		[Column("name")]
+		public string Name { get; set; } = string.Empty;
+
+		[Column("created_at")]
+		public DateTime CreatedAt { get; set; }
+
+		[Column("updated_at")]
+		public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
+
+		[Column("deleted")]
+		public bool IsDeleted { get; set; } = false;
+
+
+		[InverseProperty(nameof(ExamAttachment.Exam))]
+		public virtual ICollection<ExamAttachment> ExamAttachments { get; set; }
+		[InverseProperty(nameof(Submission.Exam))]
+		public virtual ICollection<Submission> Submissions { get; set; }
+
+		public Exam()
+		{
+			Id = Guid.NewGuid();
+
+			ExamAttachments = new HashSet<ExamAttachment>();
+			Submissions = new HashSet<Submission>();
+		}
+	}
+
+
+	public static class examExt
+	{
+		public static Submission ConvertToSubmission(this Exam exam, Guid studentId, Guid GraderId, Guid classId)
+		{
+			if (exam == null) return new Submission();
+			var submission = new Submission();
+
+			submission.StudentId = studentId;
+			submission.SubmissionTime = DateTime.Now;
+			submission.Status = SubmissionStatus.Pending;
+			submission.GraderId = GraderId;
+			submission.ExamId = exam.Id;
+			submission.ClassId = classId;
+			ConvertExamSturctToSubmissionDetails(exam.ExamStruct, studentId, submission.SubmissionDetails);
+
+			return submission;
+		}
+
+
+		public static void ConvertExamSturctToSubmissionDetails(ExamQuestion examStruct, Guid studentId, ICollection<SubmissionDetail> submissions)
+		{
+			if (examStruct == null) return;
+			submissions.Add(new SubmissionDetail
+			{
+				StudentId = studentId,
+				ExamQuestionId = examStruct.Id,
+				CreatedAt = DateTime.Now,
+				UpdatedAt = DateTime.Now,
+			});
+
+			examStruct.ChildExamQuestions?.ToList().ForEach(s =>
+			{
+				ConvertExamSturctToSubmissionDetails(s, studentId, submissions);
+			});
+		}
+	}
+}