C#怎么声明主体

如图
public class Common
{
public Common();

public static DataSet dataSet(string sqlStr);
public static DataView dataView(string sqlStr);
public static void ExecuteSql(string sqlStr);
}

用public Common(){};就行了，另外：
1.提取字段列表
/*
<%@ Import Namespace="System.Data.SqlClient"%>
*/
//<%
using(SqlConnection cn=new SqlConnection("Data Source=localhost;Initial Catalog=pubs;UserID=sa;Password=")) {
SqlCommand cmd=new SqlCommand("Select * from authors");
cn.Open();
SqlDataReader dr=cmd.ExecuteReader();
while(dr.Read()) {
Response.Write(dr("au_fname"));
}
dr.Close();
cn.Close();
}
//%>

2.返回数据集函数
/*
<%@ Import Namespace="System.Data.SqlClient"%>
*/
//<%
public DataSet GetData()
{
using(SqlConnection cn=new SqlConnection("Data Source=localhost;Initial Catalog=pubs;UserID=sa;Password="))
{
cn.Open();
SqlDataAdapter da=new SqlDataAdapter("Select * from authors",cn);
DataSet ds=new DataSet();
da.Fill(ds,"Authors");
cn.Close();