已把选课的“年级划分”和限制规则补成完整闭环：

选课批次可指定多个适用年级；留空兼容原有“全部年级”。
新增可选的“最多课程门数”，与原有学分上限并行。
年级、门数限制统一作用于学生可见批次、自主选课、候补、管理员代选和自动递补。
普通候选名单遵守年级及行政班范围；强制选课可绕过业务限制，但仍严格遵守管理员学院权限。
管理页面会展示“2026 级 · 最多 6 门 · 最多 30 学分”，名单和候补列表也增加年级列。
新增 MySQL 迁移：[CourseSelectionGradeLimits.cs](E:/jiaowu/src/Jiaowu.Api/Infrastructure/Persistence/Migrations/MySql/20260726180000_CourseSelectionGradeLimits.cs)。

src/Jiaowu.Api/Controllers/CourseSelectionsController.cs

@@ -46,7 +46,24 @@ public sealed class CourseSelectionsController(
         if (academicTermId.HasValue)
             source = source.Where(x => x.AcademicTermId == academicTermId);
         if (currentUserDataScope.Current.IsInRole(SystemRoles.Student))
+        {
+            var userId = currentUserDataScope.Current.UserId;
+            var studentGrade = await db.Students.AsNoTracking()
+                .Where(x => x.UserId == userId)
+                .Select(x => (int?)x.AdministrativeClass!.Grade)
+                .FirstOrDefaultAsync(cancellationToken);
             source = source.Where(x => x.Status != CourseSelectionRoundStatus.Draft);
+            if (studentGrade.HasValue)
+            {
+                source = source.Where(x =>
+                    !x.EligibleGrades.Any() ||
+                    x.EligibleGrades.Any(item => item.Grade == studentGrade.Value));
+            }
+            else
+            {
+                source = source.Where(_ => false);
+            }
+        }
 
         var now = DateTime.UtcNow;
         return Ok(await source
@@ -64,6 +81,10 @@ public sealed class CourseSelectionsController(
                 x.EndsAt,
                 x.WithdrawalEndsAt,
                 x.MaxCredits,
+                x.MaxCourseCount,
+                EligibleGrades = x.EligibleGrades
+                    .OrderBy(item => item.Grade)
+                    .Select(item => item.Grade),
                 x.Status,
                 IsAvailableNow =
                     x.Status == CourseSelectionRoundStatus.Open &&
@@ -76,6 +97,20 @@ public sealed class CourseSelectionsController(
             .ToListAsync(cancellationToken));
     }
 
+    [HttpGet("configuration-options")]
+    [Authorize(Roles = RoundManagers)]
+    public async Task<ActionResult> GetConfigurationOptions(
+        CancellationToken cancellationToken)
+    {
+        var grades = await db.AdministrativeClasses.AsNoTracking()
+            .Where(x => x.IsEnabled)
+            .Select(x => x.Grade)
+            .Distinct()
+            .OrderByDescending(x => x)
+            .ToListAsync(cancellationToken);
+        return Ok(new { Grades = grades });
+    }
+
     [HttpPost("rounds")]
     [Authorize(Roles = RoundManagers)]
     public async Task<ActionResult> CreateRound(
@@ -92,6 +127,10 @@ public sealed class CourseSelectionsController(
             EndsAt = request.EndsAt.ToUniversalTime(),
             WithdrawalEndsAt = request.WithdrawalEndsAt.ToUniversalTime(),
             MaxCredits = request.MaxCredits,
+            MaxCourseCount = request.MaxCourseCount,
+            EligibleGrades = NormalizeGrades(request.EligibleGrades)
+                .Select(grade => new CourseSelectionRoundGrade { Grade = grade })
+                .ToList(),
             Notes = Normalize(request.Notes)
         };
         db.CourseSelectionRounds.Add(round);
@@ -105,7 +144,9 @@ public sealed class CourseSelectionsController(
         CourseSelectionRoundRequest request,
         CancellationToken cancellationToken)
     {
-        var round = await db.CourseSelectionRounds.FindAsync([id], cancellationToken);
+        var round = await db.CourseSelectionRounds
+            .Include(x => x.EligibleGrades)
+            .FirstOrDefaultAsync(x => x.Id == id, cancellationToken);
         if (round is null) return NotFound();
         if (round.Status != CourseSelectionRoundStatus.Draft)
             return ConflictProblem("只有草稿选课批次可以修改。");
@@ -117,6 +158,20 @@ public sealed class CourseSelectionsController(
         round.EndsAt = request.EndsAt.ToUniversalTime();
         round.WithdrawalEndsAt = request.WithdrawalEndsAt.ToUniversalTime();
         round.MaxCredits = request.MaxCredits;
+        round.MaxCourseCount = request.MaxCourseCount;
+        var requestedGrades = NormalizeGrades(request.EligibleGrades);
+        var requestedGradeSet = requestedGrades.ToHashSet();
+        db.CourseSelectionRoundGrades.RemoveRange(
+            round.EligibleGrades.Where(x => !requestedGradeSet.Contains(x.Grade)));
+        foreach (var grade in requestedGrades.Where(grade =>
+                     round.EligibleGrades.All(x => x.Grade != grade)))
+        {
+            round.EligibleGrades.Add(new CourseSelectionRoundGrade
+            {
+                CourseSelectionRoundId = round.Id,
+                Grade = grade
+            });
+        }
         round.Notes = Normalize(request.Notes);
         return await SaveAsync(id, false, cancellationToken);
     }
@@ -356,6 +411,7 @@ public sealed class CourseSelectionsController(
                 x.Student.Name,
                 ClassName = x.Student.AdministrativeClass!.Name,
                 MajorName = x.Student.AdministrativeClass.Major!.Name,
+                Grade = x.Student.AdministrativeClass.Grade,
                 x.EnrolledAt
             })
             .ToListAsync(cancellationToken);
@@ -373,6 +429,7 @@ public sealed class CourseSelectionsController(
                 x.Student.Name,
                 ClassName = x.Student.AdministrativeClass!.Name,
                 MajorName = x.Student.AdministrativeClass.Major!.Name,
+                Grade = x.Student.AdministrativeClass.Grade,
                 x.WaitlistedAt
             })
             .ToListAsync(cancellationToken);
@@ -385,6 +442,7 @@ public sealed class CourseSelectionsController(
                 item.Name,
                 item.ClassName,
                 item.MajorName,
+                item.Grade,
                 item.WaitlistedAt,
                 Position = index + 1
             })
@@ -435,12 +493,17 @@ public sealed class CourseSelectionsController(
                 x.Id,
                 x.IsOpenToAll,
                 CourseNature = x.TeachingTask!.Course!.Nature,
+                CollegeId = x.TeachingTask.Course.CollegeId,
                 RoundStatus = x.CourseSelectionRound!.Status,
+                EligibleGrades = x.CourseSelectionRound.EligibleGrades
+                    .Select(item => item.Grade),
                 ClassIds = x.TeachingTask.Classes
                     .Select(item => item.AdministrativeClassId)
             })
             .FirstOrDefaultAsync(cancellationToken);
         if (offering is null) return NotFound();
+        if (!currentUserDataScope.Current.CanAccessCollege(offering.CollegeId))
+            return Forbid();
         if (!forceMode && !CourseSelectionRules.SupportsProxyEnrollment(offering.CourseNature))
             return ConflictProblem("管理员代选仅适用于公共必修课。");
         if (offering.RoundStatus == CourseSelectionRoundStatus.Draft)
@@ -453,7 +516,13 @@ public sealed class CourseSelectionsController(
                     enrollment.CourseSelectionOfferingId == id &&
                     enrollment.StudentId == x.Id &&
                     enrollment.Status == CourseEnrollmentStatus.Enrolled));
-        if (!offering.IsOpenToAll)
+        if (!forceMode && offering.EligibleGrades.Any())
+        {
+            source = source.WhereIn(
+                offering.EligibleGrades,
+                x => x.AdministrativeClass!.Grade);
+        }
+        if (!forceMode && !offering.IsOpenToAll)
             source = source.WhereIn(offering.ClassIds, x => x.AdministrativeClassId);
         if (!string.IsNullOrWhiteSpace(keyword))
         {
@@ -475,6 +544,7 @@ public sealed class CourseSelectionsController(
                 x.StudentNumber,
                 x.Name,
                 ClassName = x.AdministrativeClass!.Name,
+                Grade = x.AdministrativeClass.Grade,
                 MajorName = x.AdministrativeClass.Major!.Name,
                 CollegeName = x.AdministrativeClass.Major.College!.Name
             })
@@ -501,6 +571,7 @@ public sealed class CourseSelectionsController(
                 db.ChangeTracker.Clear();
                 var offering = await db.CourseSelectionOfferings
                     .Include(x => x.CourseSelectionRound)
+                    .ThenInclude(x => x!.EligibleGrades)
                     .Include(x => x.TeachingTask)
                     .ThenInclude(x => x!.Course)
                     .Include(x => x.TeachingTask)
@@ -526,6 +597,18 @@ public sealed class CourseSelectionsController(
                 var inactive = students.FirstOrDefault(x => x.Status != StudentStatus.Active);
                 if (inactive is not null)
                     return ConflictProblem($"学生 {inactive.StudentNumber} {inactive.Name} 当前不是在籍状态。");
+                var eligibleGrades = round.EligibleGrades
+                    .Select(x => x.Grade)
+                    .ToArray();
+                var wrongGrade = students.FirstOrDefault(student =>
+                    !CourseSelectionRules.IsGradeEligible(
+                        eligibleGrades,
+                        student.AdministrativeClass!.Grade));
+                if (wrongGrade is not null)
+                {
+                    return ConflictProblem(
+                        $"学生 {wrongGrade.StudentNumber} {wrongGrade.Name} 所在年级不属于本轮选课对象。");
+                }
                 var outOfScope = students.FirstOrDefault(student =>
                     !offering.IsOpenToAll &&
                     !task.Classes.Any(item =>
@@ -600,6 +683,20 @@ public sealed class CourseSelectionsController(
                         return ConflictProblem(
                             $"学生 {student.StudentNumber} {student.Name} 代选后将超过本轮 {round.MaxCredits:0.#} 学分上限。");
                     }
+                    var selectedCourseCount = await db.CourseEnrollments.CountAsync(
+                        x =>
+                            x.StudentId == student.Id &&
+                            x.Status == CourseEnrollmentStatus.Enrolled &&
+                            x.CourseSelectionOffering!.CourseSelectionRoundId == round.Id,
+                        cancellationToken);
+                    if (CourseSelectionRules.HasReachedCourseLimit(
+                            round.MaxCourseCount,
+                            selectedCourseCount))
+                    {
+                        return ConflictProblem(
+                            $"学生 {student.StudentNumber} {student.Name} 已达到本轮最多 " +
+                            $"{round.MaxCourseCount} 门课程限制。");
+                    }
 
                     var selectedTaskIds = await db.CourseEnrollments.AsNoTracking()
                         .Where(x =>
@@ -685,6 +782,8 @@ public sealed class CourseSelectionsController(
                 if (offering is null) return NotFound();
                 var round = offering.CourseSelectionRound!;
                 var task = offering.TeachingTask!;
+                if (!currentUserDataScope.Current.CanAccessCollege(task.Course!.CollegeId))
+                    return Forbid();
 
                 if (round.Status == CourseSelectionRoundStatus.Draft)
                     return ConflictProblem("选课批次开放后才能办理强制选课。");
@@ -769,6 +868,7 @@ public sealed class CourseSelectionsController(
                 var enrollment = await db.CourseEnrollments
                     .Include(x => x.CourseSelectionOffering)
                     .ThenInclude(x => x!.CourseSelectionRound)
+                    .ThenInclude(x => x!.EligibleGrades)
                     .Include(x => x.CourseSelectionOffering)
                     .ThenInclude(x => x!.TeachingTask)
                     .ThenInclude(x => x!.Course)
@@ -860,9 +960,19 @@ public sealed class CourseSelectionsController(
         var student = await CurrentStudentAsync(cancellationToken);
         if (student is null) return ProfileNotFound();
         var round = await db.CourseSelectionRounds.AsNoTracking()
+            .Include(x => x.EligibleGrades)
             .FirstOrDefaultAsync(x => x.Id == roundId, cancellationToken);
         if (round is null || round.Status == CourseSelectionRoundStatus.Draft)
             return NotFound();
+        var eligibleGrades = round.EligibleGrades
+            .Select(x => x.Grade)
+            .ToArray();
+        if (!CourseSelectionRules.IsGradeEligible(
+                eligibleGrades,
+                student.AdministrativeClass!.Grade))
+        {
+            return Forbid();
+        }
 
         var offerings = await db.CourseSelectionOfferings.AsNoTracking()
             .Where(x =>
@@ -968,6 +1078,8 @@ public sealed class CourseSelectionsController(
                 round.EndsAt,
                 round.WithdrawalEndsAt,
                 round.MaxCredits,
+                round.MaxCourseCount,
+                EligibleGrades = eligibleGrades,
                 round.Status,
                 IsAvailableNow = CourseSelectionRules.IsSelectionOpen(
                     round,
@@ -978,7 +1090,8 @@ public sealed class CourseSelectionsController(
                 student.Id,
                 student.StudentNumber,
                 student.Name,
-                ClassName = student.AdministrativeClass!.Name
+                ClassName = student.AdministrativeClass!.Name,
+                Grade = student.AdministrativeClass.Grade
             },
             Offerings = offerings
         });
@@ -1050,6 +1163,7 @@ public sealed class CourseSelectionsController(
 
                 var offering = await db.CourseSelectionOfferings
                     .Include(x => x.CourseSelectionRound)
+                    .ThenInclude(x => x!.EligibleGrades)
                     .Include(x => x.TeachingTask)
                     .ThenInclude(x => x!.Course)
                     .Include(x => x.TeachingTask)
@@ -1063,6 +1177,12 @@ public sealed class CourseSelectionsController(
                     return ConflictProblem("当前不在该选课批次的开放时间内。");
                 if (task.Status != TeachingTaskStatus.Published)
                     return ConflictProblem("该教学班当前不可选。");
+                if (!CourseSelectionRules.IsGradeEligible(
+                        round.EligibleGrades.Select(x => x.Grade),
+                        student.AdministrativeClass!.Grade))
+                {
+                    return ConflictProblem("你所在的年级不属于本轮选课对象。");
+                }
                 if (!offering.IsOpenToAll &&
                     !task.Classes.Any(x =>
                         x.AdministrativeClassId == student.AdministrativeClassId))
@@ -1128,6 +1248,19 @@ public sealed class CourseSelectionsController(
                         $"选课后将达到 {selectedCredits + task.Course.Credits:0.#} 学分，" +
                         $"超过本轮 {round.MaxCredits:0.#} 学分上限。");
                 }
+                var selectedCourseCount = await db.CourseEnrollments.CountAsync(
+                    x =>
+                        x.StudentId == student.Id &&
+                        x.Status == CourseEnrollmentStatus.Enrolled &&
+                        x.CourseSelectionOffering!.CourseSelectionRoundId == round.Id,
+                    cancellationToken);
+                if (CourseSelectionRules.HasReachedCourseLimit(
+                        round.MaxCourseCount,
+                        selectedCourseCount))
+                {
+                    return ConflictProblem(
+                        $"你已达到本轮最多 {round.MaxCourseCount} 门课程限制。");
+                }
 
                 // Schedule conflict check
                 var candidateEntries = await PublishedScheduleEntries(
@@ -1209,6 +1342,7 @@ public sealed class CourseSelectionsController(
 
                 var offering = await db.CourseSelectionOfferings
                     .Include(x => x.CourseSelectionRound)
+                    .ThenInclude(x => x!.EligibleGrades)
                     .Include(x => x.TeachingTask)
                     .ThenInclude(x => x!.Course)
                     .Include(x => x.TeachingTask)
@@ -1317,6 +1451,7 @@ public sealed class CourseSelectionsController(
                 var enrollment = await db.CourseEnrollments
                     .Include(x => x.CourseSelectionOffering)
                     .ThenInclude(x => x!.CourseSelectionRound)
+                    .ThenInclude(x => x!.EligibleGrades)
                     .Include(x => x.CourseSelectionOffering)
                     .ThenInclude(x => x!.TeachingTask)
                     .ThenInclude(x => x!.Course)
@@ -1504,6 +1639,11 @@ public sealed class CourseSelectionsController(
             return ValidationProblem("选课开始时间必须早于结束时间。");
         if (withdrawalEndsAt < endsAt)
             return ValidationProblem("退课截止时间不能早于选课结束时间。");
+        var eligibleGrades = NormalizeGrades(request.EligibleGrades);
+        if (eligibleGrades.Length > 20)
+            return ValidationProblem("单个选课批次最多配置 20 个适用年级。");
+        if (eligibleGrades.Any(grade => grade is < 2000 or > 2200))
+            return ValidationProblem("适用年级必须在 2000—2200 之间。");
         if (!await db.AcademicTerms.AnyAsync(
                 x => x.Id == request.AcademicTermId && x.IsEnabled,
                 cancellationToken))
@@ -1545,6 +1685,12 @@ public sealed class CourseSelectionsController(
             return new(false, "只有在籍学生可以选课或候补。");
         if (task.Status != TeachingTaskStatus.Published)
             return new(false, "该教学班当前不可选。");
+        if (!CourseSelectionRules.IsGradeEligible(
+                round.EligibleGrades.Select(x => x.Grade),
+                student.AdministrativeClass!.Grade))
+        {
+            return new(false, "你所在的年级不属于本轮选课对象。");
+        }
         if (!offering.IsOpenToAll &&
             !await db.TeachingTaskClasses.AnyAsync(
                 x =>
@@ -1591,6 +1737,20 @@ public sealed class CourseSelectionsController(
                 $"获得名额后将达到 {selectedCredits + task.Course.Credits:0.#} 学分，" +
                 $"超过本轮 {round.MaxCredits:0.#} 学分上限。");
         }
+        var selectedCourseCount = await db.CourseEnrollments.CountAsync(
+            x =>
+                x.StudentId == student.Id &&
+                x.Status == CourseEnrollmentStatus.Enrolled &&
+                x.CourseSelectionOffering!.CourseSelectionRoundId == round.Id,
+            cancellationToken);
+        if (CourseSelectionRules.HasReachedCourseLimit(
+                round.MaxCourseCount,
+                selectedCourseCount))
+        {
+            return new(
+                isRetake,
+                $"你已达到本轮最多 {round.MaxCourseCount} 门课程限制。");
+        }
 
         var candidateEntries = await PublishedScheduleEntries(
             round.AcademicTermId,
@@ -1772,6 +1932,9 @@ public sealed class CourseSelectionsController(
     private static string? Normalize(string? value) =>
         string.IsNullOrWhiteSpace(value) ? null : value.Trim();
 
+    private static int[] NormalizeGrades(IEnumerable<int>? values) =>
+        values?.Distinct().OrderBy(x => x).ToArray() ?? [];
+
     private sealed record EnrollmentEligibility(bool IsRetake, string? Error);
 }
 
@@ -1782,6 +1945,8 @@ public sealed record CourseSelectionRoundRequest(
     DateTime EndsAt,
     DateTime WithdrawalEndsAt,
     [Range(typeof(decimal), "0.5", "99")] decimal MaxCredits,
+    [Range(1, 100)] int? MaxCourseCount,
+    IReadOnlyCollection<int>? EligibleGrades,
     [MaxLength(500)] string? Notes);
 
 public sealed record CourseSelectionOfferingRequest(

src/Jiaowu.Api/Domain/Academic/CourseSelectionEntities.cs

@@ -11,12 +11,21 @@ public sealed class CourseSelectionRound : EntityBase
     public DateTime EndsAt { get; set; }
     public DateTime WithdrawalEndsAt { get; set; }
     public decimal MaxCredits { get; set; } = 30;
+    public int? MaxCourseCount { get; set; }
     public CourseSelectionRoundStatus Status { get; set; } =
         CourseSelectionRoundStatus.Draft;
     public string? Notes { get; set; }
+    public ICollection<CourseSelectionRoundGrade> EligibleGrades { get; set; } = [];
     public ICollection<CourseSelectionOffering> Offerings { get; set; } = [];
 }
 
+public sealed class CourseSelectionRoundGrade : EntityBase
+{
+    public Guid CourseSelectionRoundId { get; set; }
+    public CourseSelectionRound? CourseSelectionRound { get; set; }
+    public int Grade { get; set; }
+}
+
 public sealed class CourseSelectionOffering : EntityBase
 {
     public Guid CourseSelectionRoundId { get; set; }

src/Jiaowu.Api/Infrastructure/CourseSelection/CourseSelectionRules.cs

@@ -21,6 +21,16 @@ public static class CourseSelectionRules
     public static bool SupportsProxyEnrollment(CourseNature nature) =>
         nature == CourseNature.GeneralRequired;
 
+    public static bool IsGradeEligible(
+        IEnumerable<int> eligibleGrades,
+        int studentGrade) =>
+        !eligibleGrades.Any() || eligibleGrades.Contains(studentGrade);
+
+    public static bool HasReachedCourseLimit(
+        int? maxCourseCount,
+        int selectedCourseCount) =>
+        maxCourseCount.HasValue && selectedCourseCount >= maxCourseCount.Value;
+
     public static bool RequiresPublishedSchedule(TeachingTaskSchedulingMode schedulingMode) =>
         schedulingMode == TeachingTaskSchedulingMode.Standard;