无法在Json-MVC控制器中传递空值

如果没有值，则系统不会传递“null”值

model.SpecialtyTypeDesc = spec.SpecialtyDescription;

如果没有员工的专业值，我无法打开编辑页面。如果员工具有特定价值，则其工作罚款。如果员工的人员数据中没有任何专业知识，我希望将该值显示为Null

public JsonResult GetSpecialityDepartment(int id){
    EmployeeDepartments getDep = (from c in db.EmployeeDepartments where c.EmpId == id select c).FirstOrDefault();
    Departments dept = (from c in db.Departments where c.Id == getDep.departmentId select c).FirstOrDefault();
    EmployeeDetails details = (from c in db.EmployeeDetails where c.People_Id == id select c).FirstOrDefault();
    SpecialtyType spec = (from c in db.SpecialityType where c.SpecialtyTypeId == details.SpecialtyTypeId select c).FirstOrDefault();
    var data = new { 
        Department = dept.Name,
        SpecialtyType = spec == null ? "" : spec.SpecialtyDescription
    };

    return Json(data);
}

public ActionResult Edit(int id) {
    PersonnelLeaveAbsence leaveAbsence = (from c in db.PersonnelLeaveAbsence where c.PersonnelLeaveAbsenceId == id select c).FirstOrDefault();
    EmployeeDepartments getDep = (from c in db.EmployeeDepartments where c.EmpId == leaveAbsence.PersonnelId select c).FirstOrDefault();
    Departments dept = (from c in db.Departments where c.Id == getDep.departmentId select c).FirstOrDefault();
    EmployeeDetails details = (from c in db.EmployeeDetails where c.People_Id == leaveAbsence.PersonnelId select c).FirstOrDefault();
    SpecialtyType spec = (from c in db.SpecialtyType where c.SpecialtyTypeId == details.SpecialtyTypeId select c).FirstOrDefault();

    PersonnelLeaveAbsenceModel model = new PersonnelLeaveAbsenceModel();
    model.PersonnelLeaveAbsenceId = leaveAbsence.PersonnelLeaveAbsenceId;
    model.PersonnelLeaveDate = leaveAbsence.LeaveDate;
    model.LeaveAbsenceId = leaveAbsence.LeaveAbsenceTypeId;
    model.PersonnelId = leaveAbsence.PersonnelId;
    model.EmployeeRoleId = leaveAbsence.EmployeeRole;
    model.StartTime = leaveAbsence.StartTime;
    model.EndTime = leaveAbsence.EndTime;
    model.DayType = Convert.ToBoolean(leaveAbsence.DayType);
    model.DepartmentDesc = dept.Name;
    model.SpecialtyTypeDesc = spec.SpecialtyDescription;
}

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不传递“null”值意味着什么？如果为空，则为空！如果您的意思是要在文本为Null时显示Null，则使用属性上的[DisplayFormatNullDisplayText=Null]属性，或者将该值设置为Null。如果原始人员表中有值，则传递该值。如果原始人员表中没有专业值，代码将停止在“model.SpecialtyTypeDesc=spec.SpecialtyDescription；”。它应该显示空字段。谢谢你。你的意思是因为规格为空而得到一个异常吗？是的。异常详细信息：System.NullReferenceException:对象引用未设置为对象的实例。在问题中包含这一点很重要，你不这么认为吗。如果spec！=null{model.specialtypedesc=spec.SpecialtyDescription；}