Question

正如标题所述，我的代码片段来自我教授提供的一个例子。

我的输出是：

MagazineID Title Publisher Price SubscriptionRate 
1 People Times Inc. 4.95 19.95 
2 Car and Driver Hachetter Inc. 3.95 19.99

代码：

    private void btnShowMags_Click(object sender, EventArgs e)
    {
        // Creating new instance of the DisplayMags form.
        DisplayMags displayMags = new DisplayMags();

        // find the path where the executable resides
        string dbPath = Application.StartupPath;

        // Providing a path to the MS Access file.
        string connString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source="
            + dbPath + @"\..\..\..\..\Magazines.mdb; User Id=admin; Password=";

        // Creating a new connection and assigning it to a variable.
        OleDbConnection conn = new OleDbConnection();
        conn.ConnectionString = connString;

        // Creating a new instance for a command which we will use later.
        OleDbCommand cmd = new OleDbCommand();
        cmd.Connection = conn;

        // declare and instantiate the command
        OleDbCommand cmdMagazines = new OleDbCommand();
        cmdMagazines.CommandText = "select * from magazine";
        cmdMagazines.Connection = conn;

        OleDbDataReader drMagazines;

        try
        {
            // open the connection
            conn.Open();

            // retrieve data from the data source to the data reader
            drMagazines = cmdMagazines.ExecuteReader();

            if (drMagazines.HasRows)
            {
                // populate the column headings
                for (int i = 0; i < drMagazines.FieldCount; i++)
                    displayMags.txtDisplayMags.Text += drMagazines.GetName(i) + " ";
                displayMags.txtDisplayMags.Text += "\r\n";

                // populate the data by row
                while (drMagazines.Read())
                {
                    for (int i = 0; i < drMagazines.FieldCount; i++)
                        displayMags.txtDisplayMags.Text += drMagazines.GetValue(i) + " ";
                    displayMags.txtDisplayMags.Text += "\r\n";
                }
            }
        }
        catch (Exception ex)
        {
            // Displaying any errors that might have occured.
            MessageBox.Show("Error opening the connection: " + ex.Message + "\r\n");
        }
        finally
        {
            // Closing connection after task was completed.
            conn.Close();
        }

        // Displaying DisplayMags form, assuring that earlier form
        // will not be accessible. Show() let us access all forms.
        displayMags.ShowDialog();
    }

而且，我试图让它看起来像这样：

enter image description here

EDIT。这项工作，但这是否代表了正确的编程实践？

            if (drMagazines.HasRows)
            {
                while (drMagazines.Read())
                {
                    displayMags.txtDisplayMags.Text += "=== Magazine " + 
                        drMagazines.GetValue(0) + " ===" + Environment.NewLine + 
                        drMagazines.GetValue(1) + Environment.NewLine +
                        drMagazines.GetValue(2) + Environment.NewLine +
                        drMagazines.GetValue(3) + Environment.NewLine +
                        drMagazines.GetValue(4) + Environment.NewLine + 
                        Environment.NewLine;
                }
            }

Answer 1

我没有给你完整的答案，因为那会破坏作业的目的，你就不会学到任何东西。但是，我可以为您提供解决问题的方法。

您的输出从以if (drMagazines.HasRows)开头的块开始。该块中的代码是您进行更改所需的位置。

您需要对其进行更改，以便打印包含杂志编号，行结尾（Environment.NewLine）的分隔符，而不是打印出列标题然后打印每行的内容，然后分隔行有标题，然后有内容。

您现在的代码中包含必要的信息 - 您在populate the column headings然后populate the data by row处有评论。更改为populate a single heading然后populate the row content for that heading。建议将其从两个循环更改为一个 - 读取列标题，然后读取它包含的行内容。您可以在该循环期间为每个项目添加任何其他内容或格式。

我不理解此代码输出的格式

1 个答案: