Question

使用OleDbConnection如何连接到Access中包含20个单词的表，然后让它从表中随机选择一个单词并将其存储在表单上的标签中？

public partial class MainForm : 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|\WordsDB.accdb";


    // 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 MainForm_Load(object sender, EventArgs e)
    {
        String command = "SELECT * FROM Words";
        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);
        }
    }

    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];
            WordsLbl.Text = row["SpellingWords"].ToString();   
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error in DisplayRow : \r\n" + ex.Message);
        }
    }
}

正如您所看到的，这是代码，我想要了解的是，如何从数据库中的表中获取随机单词并将其存储在标签中？另外，我正在使用OleDbConnection来连接数据库！

Answer 1

您可以在AsEnumerable上使用DataTable，然后您可以在其中选择一个随机字词。例如，填写数据表之后：

FillDataTable(command); 
var words = myDataTable.AsEnumerable()
     .Select(d => d["word"].ToString())
     .ToList();

Random rnd = new Random();
int randomNumber = rnd.Next(0, words.Count + 1);

string randomWord = words[randomNumber];
label1.Text = randomWord;

这应该可行。您应该在此行中使用您的列名更改word：.Select(d => d["word"].ToString())

Answer 2

在我的答案中查看“拒绝修改”之后，以下是适用于原始问题的部分：

您可以尝试使用“随机”类生成如下随机数：

// =========== Get a Random Number first, then call DisplayRow() ===============

// Figure out the upper range of numbers to choose from the rows returned
int maxCount = myDataTable.Rows.Count;

// generate a random number to use for "rowIndex" in your 'myDataTable.Rows[rowIndex]'
Random randomNR = new Random();
int myRndNR = randomNR.Next(0, maxCount - 1);

// Execute your DisplayRow(int rowIndex) using myRndNR
DisplayRow(myRndNR);

// ===========

至于为什么你的程序没有工作（在评论中提到），我推荐了以下内容：

我将您的代码复制并粘贴到新项目中，并按照您的描述创建了一个Access数据库......我相信您遇到的问题是：

问题一：你的程序没有找到“WordsDB.accdb”。

可能的解决方案：

（1）你可以弄清楚如何创建正确的| DataDirectory | “连接字符串”或

中的路径

（2）将您的“WordsDB.accdb”放在一个文件夹中，您可以使用完整路径引用该文件夹，如“Data Source = C：\ inetpub \ wwwroot \ app_data \ WordsDB.accdb ”所以你的“连接字符串”如下所示：

private const String access7ConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;
Data Source=C:\inetpub\wwwroot\app_data\WordsDB.accdb";

问题二：您需要将随机代码移出当前位置，以便在填充DataTable后执行它。

可能的解决方案：

（1）将Form1.cs更改为如下所示：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.OleDb;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        // Use this connection string if your database has the extension .accdb
        private const String access7ConnectionString =
            @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\inetpub\wwwroot\app_data\WordsDB.accdb";


        // 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 MainForm_Load(object sender, EventArgs e)
        {
            String command = "SELECT * FROM Words";
            try
            {
                myConnection = new OleDbConnection(access7ConnectionString);
                myAdapter = new OleDbDataAdapter(access7ConnectionString, myConnection);
                myCommandBuilder = new OleDbCommandBuilder(myAdapter);
                myDataTable = new DataTable();
                FillDataTable(command);
                /* Move this "DisplayRow(currentRecord);" down below and use 
                   after you get a random number to pick a random word as shown
                   below... */
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

// =========== Get a Random Number first, then call DisplayRow() ===============

            // Figure out the upper range of numbers to choose from the rows returned
            int maxCount = myDataTable.Rows.Count;

            // generate a random number to use for "rowIndex" in your 'myDataTable.Rows[rowIndex]'
            Random randomNR = new Random();
            int myRndNR = randomNR.Next(0, maxCount - 1);

            // Execute your DisplayRow(int rowIndex) using myRndNR
            DisplayRow(myRndNR);

// ===========

        }

        private void FillDataTable(String selectCommand)
        {
            try
            {
                myConnection.Open();
                myAdapter.SelectCommand.CommandText = selectCommand;
                // Fill the DataTable with the rows returned 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];
                WordsLbl.Text = row["SpellingWords"].ToString();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error in DisplayRow : \r\n" + ex.Message);
            }
        }
        public Form1()
        {
            InitializeComponent();
        }
    }
}

潜在问题：

您可能没有将表单设置为执行的“事件，行为，加载”

MainForm_Load

潜在解决方案：

一个。转到Visual Studio中的“设计视图”，然后右键单击“表单”。

湾单击弹出窗口中的“属性”

℃。在“属性”窗口（可能在Visual Studio的右下角）中查找“事件”

d。找到“事件”后，查找“行为”（如果按“类别”排序属性）或“加载”（如果按字母顺序排序属性）

即在“加载”框中，确保它显示“MainForm_Load”

Answer 3

由于您正在使用访问权限，因此一旦您的数据表填充了行，就可以执行此操作。在填充数据表之后，我已经能够测试这个。我从不同的数据库填充了我的数据表，但这没关系。我的代码的最后4行可以帮助您每次从数据表中获取随机记录。

{
    const string query = "SELECT name FROM NewTable";
    var command = new SqlCommand(){CommandText = query, CommandType = System.Data.CommandType.Text,Connection=sqlConn};
    var dataAdapter = new SqlDataAdapter() { SelectCommand = command };
    DataTable dataTable = new DataTable("Names");
    dataAdapter.Fill(dataTable);

    int count = dataTable.Rows.Count; 
    int index = new Random().Next(count);

    DataRow d = dataTable.Rows[index];
    Console.WriteLine(d[0]);

}

使用OleDbConnection如何随机化单词

3 个答案: