为什么我的按钮在 c# 应用程序中不起作用 [英] why aren't my buttons working in c# application

问题描述

我有一个链接到数据库的表单，控制该表单的按钮不起作用，我没有收到任何错误，只是没有发生任何事情.

I have a form which is linked to a database and the buttons which control the form are not working, I'm not getting any errors just simply nothing is happening.

DisplayRow 类

DisplayRow class

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);
        }

    }

应该移动到下一条记录的按钮

The button which should move on to the next record

private void button1_Click(object sender, EventArgs e)
    {
        if (currentRecord < myDataTable.Rows.Count -1)
        {
            currentRecord++;
            DisplayRow(currentRecord);

        }

但就像我说的，当我运行应用程序时什么也没有发生，没有错误只是什么都没有.

But like i say when i run the app nothing happens, no errors just nothing.

按照 MyDataTable 的编码要求

as asked the coded for MyDataTable

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);
            }

        }

我正在运行的完整代码..

full code what I am running..

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 DataTable myDataTable;

    // Index of the current record
    private int currentRecord = 0;

    private void FillDataTable(string selectCommand)
    {
        currentRecord = 0;
        OleDbConnection myConnection = new OleDbConnection(access7ConnectionString);
        OleDbDataAdapter myAdapter = new OleDbDataAdapter(selectCommand, myConnection);
        myDataTable = new DataTable();


        try
        {
            myConnection.Open();
            myAdapter.SelectCommand.CommandText = selectCommand;
            myAdapter.Fill(myDataTable);
            myConnection.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error in FillDataTable : \r\n" + ex.Message);
        }
        DisplayRow(currentRecord);

    }

    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)
            //resets the index to 0 when you get past the last record
            rowIndex = 0;
        //if rowIndex is less then 0 set it to the last row
        if (rowIndex < 0)
            rowIndex = myDataTable.Rows.Count - 1;


        // 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();
        string command = "SELECT * FROM Media";
        //the try catch is in the FillDataTable method
        FillDataTable(command);
    }




    private void label2_Click(object sender, EventArgs e)
    {

    }

    private void button2_Click(object sender, EventArgs e)
    {
        //assuming this cycles through the data
        currentRecord++;
        DisplayRow(currentRecord);
    }

    private void button6_Click(object sender, EventArgs e)
    {
        //assuming this resets the data
        currentRecord = 0;
        this.DisplayRow(currentRecord);
    }

    private void button1_Click(object sender, EventArgs e)
    {
        //assuming this cycles through the data
        currentRecord++;
        DisplayRow(currentRecord);
    }
}

}

推荐答案

在 private void DisplayRow(int rowIndex) 上放置一个调试器书签，看看在调试应用程序时书签是否突出显示.如果不是，则检查您调用显示行的循环是否正确

Place a debugger bookmark on private void DisplayRow(int rowIndex) and see if bookmark get highlighted while debugging the application. if not then check if your loop for calling display row is correct

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