使用oledbdatareader C＃移至下一条记录

Question

我创建了一种方法，可以使用oledbdatareader搜索访问数据库，但是我似乎无法弄清楚如何使用按钮移至下一条记录。

请帮忙！

    private void button2_Click(object sender, EventArgs e)
    {
        System.Data.OleDb.OleDbConnection conn = new
        System.Data.OleDb.OleDbConnection();
        conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=BoilerSvc_be.mdb";
        try
        {
            conn.Open();
            OleDbCommand command = new OleDbCommand("SELECT Equipment.CustID AS CustID,Equipment.Manufacturer AS Manufacturer,Equipment.Model AS Model, Equipment.LastService AS LastService,Initial,Surname,[Address 1],[Address 2],[Address 3],[Post Town],[Post Code],Telephone FROM Contacts INNER JOIN Equipment ON Equipment.CustID = Contacts.CustID WHERE Surname = '" +  textBox12.Text + "' OR Initial = '" + textBox12.Text +  "' OR[Post Town] = '" + textBox12.Text + "' OR[Post Code] = '" + textBox12 + "'", conn);
            command.Parameters.Add(new OleDbParameter("@Name", textBox12));
            OleDbDataReader reader = command.ExecuteReader();

            while (reader.Read())
            {
                FirstName.Text = reader["Initial"].ToString();
                LastName.Text = reader["Surname"].ToString();
                Address1.Text = reader["Address 1"].ToString();
                Address2.Text = reader["Address 2"].ToString();
                Address3.Text = reader["Address 3"].ToString();
                TownCity.Text = reader["Post Town"].ToString();
                PostCode.Text = reader["Post Code"].ToString();
                Telephone.Text = reader["Telephone"].ToString();
                LstSvcDat.Text = reader["LastService"].ToString();
                BoilerMan.Text = reader["Manufacturer"].ToString();
                BoilerMod.Text = reader["Model"].ToString();
            }
            // Insert code to process data.
        }
        finally
        {
            conn.Close();
        }

Answer 1

当您调用reader.Read()时，您将reader.Read()下reader.Read()记录，这将建议您加载所需的数据，而不是根据用户输入从数据库中读取下reader.Read()记录。

这就是你的做法

应该先定义一个包含所有字段的DtoObject

public class DtoObject
{
    public string FirstName { get; set;}
    public string LastName  { get; set;}
    public string Address1  { get; set;}
    public string Address2  { get; set;}
    public string Address3  { get; set;}
    public string TownCity  { get; set;}
    public string PostCode  { get; set;}
    public string Telephone { get; set;}
    public string LstSvcDat { get; set;}
    public string BoilerMan { get; set;}
    public string BoilerMod { get; set;} 
}

然后在您的方法中添加Dto的列表，将它们加载到有效Form Inputs的方法以及向前和向后移动项目的方法

//in your class
private readonly List<DtoObject> _ls = new List<DtoObject>();
private int _currentIndex = 0;


private void LoadDto(DtoObject object)
{
    FirstName.Text = reader["Initial"].ToString();
    LastName.Text = reader["Surname"].ToString();
    ...
    BoilerMod.Text = reader["Model"].ToString();
}


private void MoveToNextItem()
{
   _currentIndex++;
   LoadDtoObject(_ls[_currentIndex]);
}

private void MoveToPreviousItem()
{
   _currentIndex--;
   LoadDtoObject(_ls[_currentIndex]);
}

然后在您的方法内部读取，只需将它们全部读取到列表中，并将值初始化为第一个索引

//clear existing data
_ls.Clear();            

while (reader.Read())
{

     var current = new DtoObject();

     current.FirstName = reader["Initial"].ToString();
     current.LastName = reader["Surname"].ToString();
     current.Address1= reader["Address 1"].ToString();
     current.Address2= reader["Address 2"].ToString();
     current.Address3= reader["Address 3"].ToString();
     current.TownCity= reader["Post Town"].ToString();
     current.PostCode= reader["Post Code"].ToString();
     current.Telephone= reader["Telephone"].ToString();
     current.LstSvcDat= reader["LastService"].ToString();
     current.BoilerMan= reader["Manufacturer"].ToString();
     current.BoilerMod= reader["Model"].ToString();  

     _ls.Add(current);
}  

//if there are any set the first values to current form
if(_ls.Any())
{
    _currentIndex = 0;
    LoadDto(_ls.First());
}
else
{
    //do something to notify no records were found
}

然后创建您的事件处理程序

private void nextItemButton_Click(object sender, EventArgs args)
{
    MoveToNextItem();
}

private void prevItemButton_Click(object sender, EventArgs args)
{
    MoveToPreviousItem();
}

Answer 2

您需要将除reader.Read()之外的所有内容移出单击处理程序。 然后，第一次单击按钮（或在启动或加载时），打开阅读器。 当有人点击该按钮，你Read纪录。

现在，您正在打开读取器，读取所有数据，然后每当有人单击按钮时关闭读取器。