Question

我创建了一个应用程序，当您使用“浏览”将音乐文件添加到应用程序时播放音乐但我的问题是我希望它与数据库连接。

我创建了一个包含信息的数据库：GeluidsfragmentDBSreal

现在我想使用列表框来显示数据库中的信息我使用了Catch and Try方法但是我的“尝试”不起作用，它直接进入我的“Catch”

我想在列表框中显示我的数据库信息。

我的数据库类

    private OleDbConnection connection;

    public DataKoppeling()
    {
        String pad;
        String provider;
        String applicatiePad;
        String connectionString;



        provider = "Provider=Microsoft.ACE.OLEDB.12.0"; 


        applicatiePad = Application.ExecutablePath.Substring(0, Application.ExecutablePath.LastIndexOf("\\"));
        pad = "Data Source=" + applicatiePad + "/GeluidsfragmentDBSreal.accdb";



        connectionString = provider + ";" + pad;

        connection = new OleDbConnection(connectionString);
    }


    public List<Geluidsfragment> GetAlleFragmenten()
    {
        String sql = "SELECT * FROM Geluidsfragment";
        OleDbCommand command = new OleDbCommand(sql, connection);

        List<Geluidsfragment> fragmenten;
        fragmenten = new List<Geluidsfragment>();

      try
        {
            connection.Open();
            OleDbDataReader reader = command.ExecuteReader();

            int nr;
            string bestandsnaam;
            string titel;
            int min;
            int sec;
            while (reader.Read())
            {
                nr = Convert.ToInt32(reader["nr"]);
                bestandsnaam = Convert.ToString(reader["Bestandsnaam"]);
                titel = Convert.ToString(reader["titel"]);
                min = Convert.ToInt32(reader["min"]);
                sec = Convert.ToInt32(reader["sec"]);
                fragmenten.Add(new Geluidsfragment(nr, bestandsnaam, titel, min, sec));
            }
        }
        catch
        {

            MessageBox.Show("foutje");
        }
        finally
        {
            connection.Close();
        }
        return fragmenten;
    }


    public void VoegToe(  int nr, string bestandsnaam , string titel ,int min ,int sec)
    {
        String sql = "INSERT INTO Geluidsfragment VALUES (" + nr + ",'" + bestandsnaam + "'" + "," + titel + "," + min + "," + sec + ")";
        OleDbCommand command = new OleDbCommand(sql, connection);

        try
        {
            connection.Open();
            command.ExecuteNonQuery();
        }
        catch
        {
        }
        finally
        {
            connection.Close();
        }
    }

    public int AantalStudenten()
    {
        String sql = "SELECT COUNT(*) FROM Geluidsfragment";
        OleDbCommand command = new OleDbCommand(sql, connection);
        int aantal = 0;
        try
        {
            connection.Open();
            aantal = Convert.ToInt32(command.ExecuteScalar());
        }
        catch
        {
        }
        finally
        {
            connection.Close();
        }
        return aantal;
    }


    }
}

Geluidsfragment class

    Public class Geluidsfragment 
    private int nr;
    private String titel;
    private int tijdsduur; //tijdsduur in seconden
    private String bestandsnaam;

    public Geluidsfragment(int nr, String bestandsnaam, String titel, int min, int sec)
    {
        this.nr = nr;
        this.bestandsnaam = bestandsnaam;
        this.titel = titel;
        this.tijdsduur = (min*60)  + sec;          
    }


    public Geluidsfragment(int nr, String bestandsnaam, String titel, int tijdsduur)
    {
        this.nr = nr;
        this.bestandsnaam = bestandsnaam;
        this.titel = "onbekend";
        this.tijdsduur = 0;
    }




    /******** properties ********************************************************/


    public int Nr
    {
        //private get; 
        get { return this.nr;}
    }


    public String Titel
    {
        get {return this.titel;}
        set { this.titel = value ;}
    }


    public int Tijdsduur
    {
        get 
        {
            return this.tijdsduur ;
        }

        set 
        {

            if (this.tijdsduur <= 0)
            {
                this.tijdsduur = 0;
            }

            else
                this.tijdsduur = value;
        }
    }



    public string TijdsduurString
    {
        get 
        {


            int minuten = (tijdsduur / 60);
            int seconden = (tijdsduur % 60);

            return String.Format("{0:00} : {1:00} ", minuten , seconden);       
        }

    }


    public string Bestandsnaam
    {
        get { return this.bestandsnaam; }
        set { this.bestandsnaam = value; }
    }
    public String toonInfo()
    {
        return nr.ToString() + " - " + titel + " - " + tijdsduur.ToString() + " - " + bestandsnaam;
    }

    public String AlsString()
    {


       return String.Format("Nr {0}: {1} - {2:0.00} ", nr, titel,TijdsduurString); 
    }


    public bool Play()
    {
        try
        {
            System.Media.SoundPlayer myPlayer = new System.Media.SoundPlayer();
            myPlayer.SoundLocation = bestandsnaam;
            myPlayer.Play();
            return true;
        }
        catch
        {
            return false;
        }

    }
}

}

BG体验课

{


    public List<Geluidsfragment> fragmenten; 
    private String thema;

    public BGExperience(String thema)
    {
        fragmenten = new List<Geluidsfragment>();
        this.thema = thema;
    }


    public String Thema
    {
        get { return Thema; }
    }


    public Geluidsfragment GetFragment(int nr)
    {
        foreach (Geluidsfragment fragment in fragmenten)
        {
            if (fragment.Nr == nr)
            {
                return fragment;
            }
        }

        return null;
    }



   public List<Geluidsfragment> GetAlleFragmenten()
    {
        return fragmenten;
    }


    public List<Geluidsfragment> GetFragment(String p)
    {
        List<Geluidsfragment> resultaten = new List<Geluidsfragment>();

        foreach (Geluidsfragment fragment in fragmenten)
        {
            if (fragment.Titel.IndexOf(p) != -1)
            {
                resultaten.Add(fragment);
            }
        }

        return resultaten;
    }

    public bool AddFragment(int nr, String bestandsnaam, String titel, int min, int sec)
    {
        foreach (Geluidsfragment fragment in fragmenten)
        {
               if (fragment.Nr == nr)
            {
                MessageBox.Show("Het nummer is al in gebruik");
                return false;
            }
        }
         if (min <= 0)

                if (sec <= 0)
                {
                    MessageBox.Show("Beide getallen mogen niet 0 zijn");
                return false;
            }
            else

                if (sec <= 0)

                    if (min <= 0)
                    {
                        MessageBox.Show("Beide getallen mogen niet 0 zijn");
                    return false;
                }
                else if (min <= 00)

                    if (sec <= 00)
                    {
                        MessageBox.Show("Beide getallen mogen niet 0 zijn");
                    return false;
                }
                         else

                if (sec <= 00)
                {
                    if (min <= 00)
                    {
                        MessageBox.Show("Beide getallen mogen niet 0 zijn");
                        return false;
                    }
    }
                    if (sec > 60)
                    {
                        MessageBox.Show("Seconden mag max 60 zijn");
                        return false;
                    }

            fragmenten.Add(new Geluidsfragment(nr, bestandsnaam, titel, min, sec));

            return true;
        }

    }
}

我的表单中需要数据库信息的按钮（nr，titel，min，sec，bestandsnaam） {

        private void Database_Click(object sender, EventArgs e) 
        List muziek; muziek = dk.GetAlleFragmenten();
        listBox1.Items.Clear();
        foreach (Geluidsfragment fragment in muziek)
        {
            listBox1.Items.Add(fragment.AlsString());
        }


    }

Answer 1

.Open（）方法有问题。在连接字符串中提到的位置检查连接字符串和数据库是否可用。最可能的原因是@RecerNerd在评论中提到的内容。

@Ken白色信息将有用，如果你把

catch (Exception ex)
{
  MessageBox.Show(ex.StackTrace)
}

Answer 2

我总是使用这个连接类进行数据库连接，你可以试试这个：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace dailyNotes
{
class create_connection
{
    public static SqlConnection CreateConnection()
    {
        string ConnString = @"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\Hizbul Bahar\Documents\dailynotes.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True";
        SqlConnection Conn = new SqlConnection(ConnString);
        Conn.Open();
        return Conn;
    }
        public void disconnect(SqlConnection conn)
        {
            conn.Close();
        }
    }

}

将c＃与数据库连接

2 个答案: