每次在后台代码里都要加上 using System.Data.SqlClient,该如何解决

using System;using System.Data;using System.Configuration;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Data.SqlClient;using System.Threading;/// <summary>/// database 的摘要说明/// </summary>public class database{    public database()    {        //        // TODO: 在此处添加构造函数逻辑        //    }    public string MassageBox(string TxtMassage) {        string str;        str = "<script language=javascript>alert('" + TxtMassage + "')</script>";        return str;    }    public Boolean Exect(string sQueryString) {        SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["conStr"]);        conn.Open();        SqlCommand cmd = new SqlCommand(sQueryString, conn);        try        {            cmd.ExecuteNonQuery();            conn.Close();        }        catch (System.Exception e) {            conn.Close();            return false;        }        return true;    }    public System.Data.DataSet GetDataSet(string sQueryString, string TableName) {        SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["conStr"]);        conn.Open();        SqlDataAdapter dbAdapter = new SqlDataAdapter(sQueryString, conn);        DataSet ds = new DataSet();        dbAdapter.Fill(ds, TableName);        conn.Close();        return ds;    }}