爲什麼我的C＃代碼只顯示數據庫中的第一行？

Question

我的目標

嗨，我試圖代碼，我想從一個名爲FruitsDatabase.accdb一個Microsoft Access 2016數據庫名爲Fruits_Table表檢索值C＃應用程序。然後我想在我的表單中的標籤中顯示這些值，分別稱爲label1，label2，label3。

僅供參考，我在名爲「Fruits.cs」的另一個類文件中使用了名爲Fruit（構造函數，字符串名稱，字符串顏色）的構造函數。然後我將這個構造函數傳入我的PresentationGUI表單。

我的數據庫

數據庫有一個名爲Fruits_Table一個表，該表中有兩列：「名稱」爲水果的名稱和「顏色」的顏色。數據庫中記錄了三項：蘋果 - 紅色，香蕉 - 黃色，梨 - 綠色。

我設法得到工作至今

我設法讓我的數據庫連接成功。所以沒有必要爲此擔心。從數據庫檢索值也很好。

我的問題

我的問題是這樣的：

只有在我的數據庫中的第一個條目似乎顯示，無論我點擊其中的水果圖片框。換句話說，無論我點擊picBox1，picBox2還是picBox3，它都會顯示'Apple'和'Red'

我該如何去遍歷數據庫的行？

using System; 
... 
using system.Windows.Forms; 
using system.Data.OleDb; 

namespace project1 
{ 
    public partial class PresentationGUI : Form 
    { 
      private OleDbConnection aConn; 
      private OleDbCommand aCmd; 
      private OleDbDataReader aReader; 

      private string aConnection; 
      private string sql; 

      Fruit[] aFruit = new Fruit[10]; 

    public PresentationGUI() 
    { 
      Initialize Component; 

      //This is working fine. 
      aConnection = "Provider = Microsoft.ACE.OLEDB.12.0; Data Source = FruitsDatabase.accdb;"; 

      sql = "SELECT * FROM Fruits_Table"; 
      aCmd = new OleDbCommand(); 
      aCmd.CommandText = sql; 

      aCmd.Connection = aConn; 
      aReader = aCmd.ExecuteReader(); 

      while (aReader.Read()) 
      { 

      //I have a Fruit constructor that goes: Fruit(string Name, string Color) in another class named Fruit.cs, and I use it here for this form. 
      aFruit[0] = new Fruit(aReader["Name"].ToString(), aReader["Color"].ToString()); 
      aFruit[1] = new Fruit(aReader["Name"].ToString(), aReader["Color"].ToString()); 
      aFruit[2] = new Fruit(aReader["Name"].ToString(), aReader["Color"].ToString()); 
      } 

    private void PresentationGUI_Load(object sender, EventArgs e) {...} 

    //Intended Output: when the user clicks on picBox1 (showing an image of an apple) it should display 'Apple' for label1 and 'red' for label2 
    //Reality: it displays 'Apple' for label1 and 'Red' for label2 
    private void picBox1_Click(object sender, EventArgs e) 
    { 
     try 
     { 
       this.label1.Text = aFruit[0].Name.ToString(); 
       this.label2.Text = aFruit[0].Color.ToString(); 
     } 
     catch (NullReferenceException) {....} 
    } 

    //Intended Output: when the user clicks on picBox2 (showing an image of an Banana) it should display 'Banana' for label1 and 'yellow' for label2 
    //Reality: it displays 'Apple' for label1 and 'Red' for label2 
    private void picBox2_Click(object sender, EventArgs e) 
    { 
     try 
     { 
       this.label1.Text = aFruit[1].Name.ToString(); 
       this.label2.Text = aFruit[1].Color.ToString(); 
     } 
     catch (NullReferenceException) {....} 
    } 

    //Intended Output: when the user clicks on picBox2 (showing an image of an Pear) it should display 'Pear' for label1 and 'green' for label2 
    //Reality: it displays 'Apple' for label1 and 'Red' for label2 
    private void picBox3_Click(object sender, EventArgs e) 
    { 
     try 
     { 
       this.label1.Text = aFruit[2].Name.ToString(); 
       this.label2.Text = aFruit[2].Color.ToString(); 
     } 
     catch (NullReferenceException) {....} 
    } 

    } 
}  

爲什麼它只顯示我的數據庫的第一行？

Answer 1

您正在加載相同的值到您的陣列三次，所以請嘗試更改雖然聲明是這樣的：

int fruitCounter = 0 
while (aReader.Read()) 
{ 
    //I have a Fruit constructor that goes: Fruit(string Name, string Color) in another class named Fruit.cs, and I use it here for this form. 
    aFruit[fruitCounter] = new Fruit(aReader["Name"].ToString(), aReader["Color"].ToString()); 
    fruitCounter++; 

    if(fruitCounter > aFruit.Length) 
    { 
      break; 
    } 
} 

我建議你第一次進入您的查詢返回的行數和然後根據該值初始化您的數組。