C#通过ADO.NET访问数据的方法详解

string connectionString = "server=your_server;database=your_database;user id=your_user;password=your_password;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
    try
    {
        connection.Open();
        Console.WriteLine("数据库连接成功！");
        // 在这里进行后续的数据操作
    }
    catch (SqlException ex)
    {
        Console.WriteLine("数据库连接错误: " + ex.Message);
    }
}

string query = "select * from Employees";
using (SqlCommand command = new SqlCommand(query, connection))
{
    SqlDataReader reader = command.ExecuteReader();
    while (reader.Read())
    {
        Console.WriteLine(reader["EmployeeName"].ToString());
    }
    reader.Close();
}

string insertQuery = "insert into Employees (EmployeeName, Department) values ('John Doe', 'HR')";
using (SqlCommand insertCommand = new SqlCommand(insertQuery, connection))
{
    int rowsAffected = insertCommand.ExecuteNonQuery();
    Console.WriteLine(rowsAffected + " 行数据已插入。");
}

string updateQuery = "update Employees set Department = 'IT' where EmployeeName = 'John Doe'";
using (SqlCommand updateCommand = new SqlCommand(updateQuery, connection))
{
    int rowsAffected = updateCommand.ExecuteNonQuery();
    Console.WriteLine(rowsAffected + " 行数据已更新。");
}

string deleteQuery = "delete from Employees where EmployeeName = 'John Doe'";
using (SqlCommand deleteCommand = new SqlCommand(deleteQuery, connection))
{
    int rowsAffected = deleteCommand.ExecuteNonQuery();
    Console.WriteLine(rowsAffected + " 行数据已删除。");
}

string selectQuery = "select * from Employees";
using (SqlDataAdapter adapter = new SqlDataAdapter(selectQuery, connection))
{
    DataSet dataset = new DataSet();
    adapter.Fill(dataset, "Employees");
    DataTable table = dataset.Tables["Employees"];
    foreach (DataRow row in table.Rows)
    {
        Console.WriteLine(row["EmployeeName"].ToString());
    }

try
{
    // 数据库操作代码
    string connectionString = "server=your_server;database=your_database;user id=your_user;password=your_password;";
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        string query = "select * from Employees";
        using (SqlCommand command = new SqlCommand(query, connection))
        {
            SqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                Console.WriteLine(reader["EmployeeName"].ToString());
            }
            reader.Close();
        }
    }
}
catch (SqlException ex)
{
    Console.WriteLine("数据库错误: " + ex.Message);
}
finally
{
    // 这里可以添加释放资源的代码，如关闭连接等
}