c# - 遍历数据库表行 C#

Question

我的数据库中有一个名为 students 的表，其中包含编号、姓名、地址....
我有一个表格，我一次加载一个学生的所有信息，我有一个下一步按钮和一个后退按钮。
我如何迭代到 mysql 中的下一行(或上一行)(以便能够看到下一个学生的信息)？
我尝试使用主键(自动递增)进行迭代，当我想查看下一条记录时，我将 id 加 1 或减 1 以查看上一条记录。
但是，如果删除一条记录，它将显示一条空记录。你能给我指出正确的方向吗？
我使用 WinForms
对不起我的英语..

            string config = "server=localhost; userid = root; database = databaseName";
            MySqlConnection con = new MySqlConnection(config);

            MySqlDataReader reader = null;
            string query = "SELECT * FROM students WHERE id = " + id; //id is the primary Key (auto increment)

            MySqlCommand command = new MySqlCommand(query, con);
            con.Open();
            reader = command.ExecuteReader();

            while (reader.Read())
            {

                string studentName = (string)reader["studentName"];

                string studentNum = (string)reader["studentNum"];

                tbstudentName.Text = Convert.ToString(studentName);
                tbstudentNum.Text = Convert.ToString(studentNum);                   

                .....
            }
            con.Close();

Answer 1

您不应该在每次要查看下一条记录时都调用数据库。尝试将所有数据读入列表。

我不确定您使用的是什么.. WinForms？白皮书？

如果是 WinForms，您将需要执行类似的操作。

    public class Student
    {//First create a class to hold your data in
      public string Name { get; set; }
      public string Num { get; set; }
    }

public class MyForm : Form
{
    int Index = 0;
    List<Student> FormData { get; set; }

    void GetData()
    {
    //This will hold all your data in memory so you do not have to make a database call each and every "iteration"
    List<Student> dbData = new List<Student>();

    string config = "server=localhost; userid = root; database = databaseName";
        MySqlConnection con = new MySqlConnection(config);

        MySqlDataReader reader = null;
        string query = "SELECT * FROM students";

        MySqlCommand command = new MySqlCommand(query, con);
        con.Open();
        reader = command.ExecuteReader();

        while (reader.Read())
        {
            Student newStudent = new Student();

            newStudent.Name = (string)reader["studentName"];

            newStudent.Num = (string)reader["studentNum"];
            //Add data to the list you created
            dbData.Add(newStudent);          

            .....
        }
        con.Close();

        //set the Form's list equal to the one you just populated
        this.FormData = dbData;
    }

    private void BindData()
    {
        //If winforms
        tbstudentName.Text = FormData[Index].Name;
        tbstudentNum.Text = FormData[Index].Num;

        //If wpf you will have to use view models and bind your data in your XAML but I am assuming you are using
        //winforms here.
    }

    private void NextRecord()
    {    //If you reached the end of the records then this will prevent IndexOutOfRange Exception
        if (Index < FormData.Count - 1)
        {
            Index++;
            BindData();
        }
    }

    private void PreviousRecord()
    {
        if (Index != 0)
        {
            Index--;
            BindData();
        }
    }
}

现在上面的场景将让它快速工作；但是，有更好的方法可以在您需要更改该数据时帮助您。我会推荐 WinForms 绑定(bind)。你可以在这里查看 http://msdn.microsoft.com/en-us/library/c8aebh9k(v=vs.110).aspx