镇江阿里云代理商：access 数据库 c# 操作类

以下是一个示例代码，用于在 C# 中操作 Access 数据库：

using System.Data.OleDb;

class AccessDB
{
    // 数据库连接字符串
    private readonly string connectionString;

    public AccessDB(string filepath)
    {
        connectionString = $"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={filepath};Persist Security Info=False;";
    }

    // 查询语句示例
    public void PerformQuery()
    {
        using (OleDbConnection connection = new OleDbConnection(connectionString))
        {
            OleDbCommand command = new OleDbCommand("SELECT * FROM myTable", connection);
            connection.Open();
            OleDbDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                // 处理每一行数据
                string column1Value = reader.GetString(0);
                int column2Value = reader.GetInt32(1);
                // ...
            }
            reader.Close();
        }
    }

    // 插入语句示例
    public void PerformInsert()
    {
        using (OleDbConnection connection = new OleDbConnection(connectionString))
        {
            OleDbCommand command = new OleDbCommand("INSERT INTO myTable (column1, column2) VALUES (?, ?)", connection);
            command.Parameters.AddWithValue("?", "value1");   // 第一个参数的值
            command.Parameters.AddWithValue("?", 123);       // 第二个参数的值
            connection.Open();
            command.ExecuteNonQuery();
        }
    }

    // 更新语句示例
    public void PerformUpdate()
    {
        using (OleDbConnection connection = new OleDbConnection(connectionString))
        {
            OleDbCommand command = new OleDbCommand("UPDATE myTable SET column1 = ? WHERE id = ?", connection);
            command.Parameters.AddWithValue("?", "new value");  // 要更新的值
            command.Parameters.AddWithValue("?", 1);           // WHERE 子句中的参数值
            connection.Open();
            command.ExecuteNonQuery();
        }
    }

    // 删除语句示例
    public void PerformDelete()
    {
        using (OleDbConnection connection = new OleDbConnection(connectionString))
        {
            OleDbCommand command = new OleDbCommand("DELETE FROM myTable WHERE id = ?", connection);
            command.Parameters.AddWithValue("?", 1);   // WHERE 子句中的参数值
            connection.Open();
            command.ExecuteNonQuery();
        }
    }
}

在实际应用中，需要根据具体情况修改连接字符串和 SQL 语句，以适应不同的 Access 数据库。

以下是利用C#操作Access数据库的示例代码：

using System.Data.OleDb;

public class AccessHelper
{
    private static string connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:datadatabase.mdb";
    private static OleDbConnection oleDbConnection;

    //打开数据库连接
    public static void Open()
    {
        oleDbConnection = new OleDbConnection(connectionString);
        if (oleDbConnection.State == System.Data.ConnectionState.Closed)
            oleDbConnection.Open();
    }

    //关闭数据库连接
    public static void Close()
    {
        if (oleDbConnection.State == System.Data.ConnectionState.Open)
            oleDbConnection.Close();
    }

    //执行SQL语句，返回受影响的行数
    public static int ExecuteNonQuery(string sql)
    {
        Open();
        OleDbCommand cmd = new OleDbCommand(sql, oleDbConnection);
        int affected = cmd.ExecuteNonQuery();
        Close();
        return affected;
    }

    //执行SQL语句，返回查询到的第一行第一列的值
    public static object ExecuteScalar(string sql)
    {
        Open();
        OleDbCommand cmd = new OleDbCommand(sql, oleDbConnection);
        object result = cmd.ExecuteScalar();
        Close();
        return result;
    }

    //执行SQL语句，返回查询到的结果集
    public static OleDbDataReader ExecuteReader(string sql)
    {
        Open();
        OleDbCommand cmd = new OleDbCommand(sql, oleDbConnection);
        OleDbDataReader reader = cmd.ExecuteReader();
        return reader;
    }
}

其中，connectionString是连接Access数据库的字符串，根据实际情况修改即可。Open()和Close()方法分别用于打开和关闭数据库连接。ExecuteNonQuery(string sql)方法执行给定的SQL语句并返回受影响的行数。ExecuteScalar(string sql)方法执行给定的SQL语句并返回查询到的第一行第一列的值。ExecuteReader(string sql)方法执行给定的SQL语句并返回查询到的结果集。使用方法如下：

string sql = "SELECT * FROM users WHERE username='admin'";
OleDbDataReader reader = AccessHelper.ExecuteReader(sql);
while (reader.Read())
{
    string username = reader.GetString(reader.GetOrdinal("username"));
    string password = reader.GetString(reader.GetOrdinal("password"));
    Console.WriteLine("username: " + username + ", password: " + password);
}
reader.Close();