从文本文件中读取不起作用

Question

对于我的代码，有3个列表集合。保存员工(具有名称/id参数)和服务请求(包含参数名称/id/description)的人。然后，第三个任务是从其他2个列表中保存员工和服务请求的任务(将雇员分配给服务请求)。

我已经读取了为员工/服务请求工作的内容，但是对于任务，我得到了一个错误：“对象引用没有设置为对象的实例”。当我运行我的代码时，我不知道如何修复它。

assignment.Employee.Name = columns[0];的错误点--我在想，可能类似于//assignment.Employee = columns[0]; --将整个employee对象分配给列。但是，它给出了不能将字符串转换为MaintenanceManagementSystem.Employee的错误。

/Code用于阅读员工。

    public static List<Employee> GetEmployees()
    {
        if (!Directory.Exists(dir))
            Directory.CreateDirectory(dir);

        StreamReader textIn =
            new StreamReader(
                new FileStream(path1, FileMode.OpenOrCreate, FileAccess.Read));

        List<Employee> employees = new List<Employee>();

        while (textIn.Peek() != -1)
        {
            string row = textIn.ReadLine();
            string[] columns = row.Split('|');
            Employee employee = new Employee();
            employee.Name = columns[0];
            employee.ID = columns[1];
            employees.Add(employee);
        }

        textIn.Close();

        return employees;
    }

/阅读请求代码

    public static List<ServiceRequest> GetRequest()
    {
        if (!Directory.Exists(dir))
            Directory.CreateDirectory(dir);

        StreamReader textIn =
            new StreamReader(
                new FileStream(path2, FileMode.OpenOrCreate, FileAccess.Read));

        List<ServiceRequest> serviceRequests = new List<ServiceRequest>();

        while (textIn.Peek() != -1)
        {
            string row = textIn.ReadLine();
            string[] columns = row.Split('|');
            ServiceRequest serviceRequest = new ServiceRequest();
            serviceRequest.Name = columns[0];
            serviceRequest.ID = columns[1];
            serviceRequest.Desc = columns[2];
            serviceRequests.Add(serviceRequest);
        }

        textIn.Close();

        return serviceRequests;
    }

/阅读作业守则

public static List<Assignment> GetAssignment()
    {
        if (!Directory.Exists(dir))
            Directory.CreateDirectory(dir);

        StreamReader textIn =
            new StreamReader(
                new FileStream(path3, FileMode.OpenOrCreate, FileAccess.Read));

        List<Assignment> assignments = new List<Assignment>();

        while (textIn.Peek() != -1)
        {
            string row = textIn.ReadLine();
            string[] columns = row.Split('|');
            Assignment assignment = new Assignment();
            //Employee employee = new Employee();
            //assignment.Employee = columns[0];
            assignment.Employee.Name = columns[0];
            assignment.Employee.ID = columns[1];
            //assignment.Request = columns[1];
            assignment.Request.Name = columns[2];
            assignment.Request.ID = columns[3];
            assignment.Request.Desc = columns[4];
            assignments.Add(assignment);
        }

        textIn.Close();

        return assignments;
    }
}

//代码，它在表单加载时从文本文件中读取

 private void ManagerStart_Load(object sender, EventArgs e)
    {
        myAssignments.Employees = FileIO.GetEmployees();
        myRequest.Requests = FileIO.GetRequest();
        myAssignments.Assignments = FileIO.GetAssignment();
        lstEmployee.Items.Clear();
        lstServiceRequest.Items.Clear();
        foreach (Employee employee in myAssignments.Employees)
        {
            lstEmployee.Items.Add(employee.ToString());
        }

        foreach (ServiceRequest serviceRequest in myRequest.Requests)
        {
            lstServiceRequest.Items.Add(serviceRequest.ToString());
        }

        foreach (Assignment assignment in myAssignments.Assignments)
        {
            lstAssignments.Items.Add(assignment.ToString());
        }
    }         

Answer 1

您必须创建属于Employee和Request的Assignment实例，无论是在Assignment构造函数中还是在外部。

public class Assignment
{
  public Employee Employee { get; set; }
  public Request Request { get; set; }
  public Assignment()
  {
    Employee = new Employee();
    Request = new Request();
  }
}

或

Assignment assignment = new Assignment() {
  Employee = new Employee(),
  Request = new Request()
};