c# - 从阅读器打印出多行

Question

下面将从数据库中打印出 1 行

public partial class Default : System.Web.UI.Page
{
    SqlConnection connection;
    SqlCommand command;
    SqlDataReader reader;

    protected void Page_Load(object sender, EventArgs e)
    {
        using (connection = new SqlConnection(ConfigurationManager.AppSettings["connString"]))
        {
            using (command = new SqlCommand("select col1, col2 from table1 where id = @id", connection))
            {
                command.Parameters.Add("@id", SqlDbType.Int, 3).Value = 1;
                connection.Open();

                using (reader = command.ExecuteReader())
                {
                    reader.Read();
                    Div1.InnerHtml = reader["col1"].ToString();
                }
            }
        }
    }
}

这里需要做什么才能打印出所有返回的行？

Answer 1

这里:

using (reader = command.ExecuteReader())
{
    var sb = new StringBuilder();
    while (reader.Read())
    {
        sb.Append(reader["col1"].ToString());
    }
    Div1.InnerHtml = sb.ToString();
}

此外，由于您是在方法中实例化连接对象，因此您实际上并不需要将它们设为私有(private)字段:

public partial class Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        using (var connection = new SqlConnection(ConfigurationManager.AppSettings["connString"]))
        using (var command = new SqlCommand("select col1, col2 from table1 where id = @id", connection))
        {
            command.Parameters.Add("@id", SqlDbType.Int, 3).Value = 1;
            connection.Open();

            using (var reader = command.ExecuteReader())
            {
                var sb = new StringBuilder();
                while (reader.Read())
                {
                    sb.Append(reader.GetString(reader.GetOrdinal("col1")));
                }
                Div1.InnerHtml = sb.ToString();
            }
        }
    }
}