如果在foreach中出现错误，继续插入

我有一个嵌套列表，我正在迭代它并将数据插入到我的数据库中，只有当所有子列表项都成功插入到数据库中。

你可以看到我的代码，我使用try catch嵌套迭代，以及外部迭代和整个代码被包装在BeginTransaction.

只要我提供有效的数据，这段代码就可以正常工作。

但是，如果嵌套迭代失败，由于一些验证问题(i.e. SubjectCategoryId not provided )，它在做所有迭代后退出内部foreach，增加外部foreach，尝试执行SaveChanges，但说对象Null引用错误失败。

如果你需要更多的信息，尽管问我。我觉得我遗漏了一些要点，特别是在处理BeginTransaction中的嵌套foreach时。

你看到我的代码结构有什么问题吗?我用EF 5

我代码:

foreach (var student in Student)
{
    using (var transaction = _context.Database.BeginTransaction())
    {
        try
        {
            Student student = new Student
            {
                StudentNo = item.Stu_No,
                Name = item.FullName,
                Description = item.Description,
                Phone = item.ContactNo,
                Address = item.Location
                Status =  item.status
            };
            _context.Student.Add(student);
            _context.SaveChanges(); // Get Object Null reference error for second iteration if child iteration fails. But works fine if no data issue.
             var subjectsInfo = student.Subject_Info.GroupBy(pt => new { pt.Subject_Id, pt.SubjectDesc }).ToList();
             SubjectInfo subInfo = new SubjectInfo();
             SubjectCategory subCat = new SubjectCategory();
             foreach(var subjectInfo in subjectsInfo)
             {
                 try
                 {
                    subInfo.Subject_Id = subjectInfo.Id;
                    subInfo.Description = subjectInfo.Description;
                    subInfo.Id = student.Id;
                    _context.SubjectInfo.Add(subInfo);
                    _context.saveChanges();
                    subCat.SubjectCategoryId = subjectInfo.SubjectCategoryId;
                    subCat.Status = subjectInfo.Status;
                    _context.SubjectCategory.Add(subCat);
                    _context.saveChanges();
                 }
                 Catch(Exception ex)
                 {
                      // catch exception
                 }
             }
        }
        Catch(Exception ex)
        {
        }
    } 
}

My data population:

List<Student> Student= new List<Student>();
Student.Add(new Student
{
    BasicInfo = new BasicInfo
    {
        Stu_No = "1",
        FullName = "Steve Adam",
        ContactNo = "12345",
        Location = "XYZ",
        Status = "Active",
    },
    Subject_Info = new List<Subject_Info>
    {
        new Subject_Info() {
        Subject_Id = "1",
        SubjectDesc = "Math",
        SubjectCategoryId = "",
        Status = active
        },
        new Subject_Info() {
        Subject_Id = "2",
        SubjectDesc = "Physics",
        SubjectCategoryId = "",
        Status = active
        },
    }
});

foreach (var student in Student)
{
    using (var transaction = _context.Database.BeginTransaction())
    {
        try
        {
            Student student = new Student...

foreach (var student in Student)
{
    using (var transaction = _context.Database.BeginTransaction())
    {
        try
        {
            Student student = new Student...
            int numSuccesses = 0;
             foreach(var subjectInfo in subjectsInfo)
             {
                 try
                 {
                   ... code omitted for clarity
                   numSuccesses++; // The very last thing you do
                 }     
                 Catch(Exception ex)
                 {
                  // catch exception
                 }
             }
        }
        Catch(Exception ex)
        {
        }
    } 
}

if (numSucesses == 0)
{
    // Roll back the insertion of the student record
}