我有一个简单的表单，它连接到访问数据库并显示记录，这段代码显示了发生了什么，为什么我试图编码的按钮不起作用？我猜它与我没有正确清除的变量有关？
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
namespace MediaPlayer
{
public partial class Media : Form
{
// Use this connection string if your database has the extension .accdb
private const String access7ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\MediaDatabase.accdb";
// Use this connection string if your database has the extension .mdb
private const String access2003ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\MediaDatabase.mdb";
// Data components
private OleDbConnection myConnection;
private DataTable myDataTable;
private OleDbDataAdapter myAdapter;
private OleDbCommandBuilder myCommandBuilder;
// Index of the current record
private int currentRecord = 0;
private void FillDataTable(String selectCommand)
{
try
{
myConnection.Open();
myAdapter.SelectCommand.CommandText = selectCommand;
// Fill the datatable with the rows reurned by the select command
myAdapter.Fill(myDataTable);
myConnection.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error in FillDataTable : \r\n" + ex.Message);
}
}
private void DisplayRow(int rowIndex)
{
// Check that we can retrieve the given row
if (myDataTable.Rows.Count == 0)
return; // nothing to display
if (rowIndex >= myDataTable.Rows.Count)
return; // the index is out of range
// If we get this far then we can retrieve the data
try
{
DataRow row = myDataTable.Rows[rowIndex];
textBox1.Text = row["FilePath"].ToString();
textBox2.Text = row["Subject"].ToString();
textBox3.Text = row["Title"].ToString();
textBox4.Text = row["Keywords"].ToString();
textBox5.Text = row["MediaType"].ToString();
}
catch (Exception ex)
{
MessageBox.Show("Error in DisplayRow : \r\n" + ex.Message);
}
}
public Media()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
{
String command = "SELECT * FROM Media";
try
{
myConnection = new OleDbConnection(access7ConnectionString);
myAdapter = new OleDbDataAdapter(access7ConnectionString, myConnection);
myCommandBuilder = new OleDbCommandBuilder(myAdapter);
myDataTable = new DataTable();
FillDataTable(command);
DisplayRow(currentRecord);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
int m_rowPosition = 0;
private void label2_Click(object sender, EventArgs e)
{
}
private void button2_Click(object sender, EventArgs e)
{
//if not at the first row, go back one row and show the record.
if (m_rowPosition !=0)
{
m_rowPosition---;
this.DisplayRow();
}
}
private void button6_Click(object sender, EventArgs e)
{
//move to first row of data and show data
m_rowPosition = 0;
this.DisplayRow();
}
}
}