有关asp编程中，baseclass的问题

using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

public partial class Admin_Addclass : System.Web.UI.Page
{
SqlConnection conn = BaseClass.DBCon();
protected void Page_Load(object sender, EventArgs e)
{
string str = "select * from tb_teacher";
BaseClass.BindDDL(DDltcr, "TeacherName", "TeacherID", str, "tb_teacher");
string str1 = "select * from tb_professional";
BaseClass.BindDDL(DDlpsl, "ProfessionalName", "professionalID", str1, "tb_professional");
string str2 = "select * from tb_department";
BaseClass.BindDDL(DDlatt, "DepartmentName", "DepartmentID", str2, "tb_department");

}
protected void btnOK_Click(object sender, EventArgs e)
{
string str = "insert into tb_class(ClassID,ClassName,StudenNumber,Grade,ProfessionalID,DepartmentID,ManagerID,ClassDescription) values('" + txtclsID.Text.Trim() + "','" + txtclsNum.Text.Trim() + "','" + txtNbr.Text.Trim() + "','" + txtge.Text.Trim() + "','" + DDlpsl.SelectedValue.Trim() + "','" + DDlatt.SelectedValue.Trim() + "','" + DDltcr.SelectedValue.Trim() + "','" + txtmrID.Text.Trim() + "')";
SqlCommand cmd = new SqlCommand(str, conn);
conn.Open();
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
Response.Write("<script>alert('插入成功！');</script>");
}
}
protected void btnEsc_Click(object sender, EventArgs e)
{
txtclsID.Text = "";
txtclsNum.Text = "";
txtge.Text = "";
txtmrID.Text = "";
txtNbr.Text = "";
}
}

在这段代码中，一直提示baseclass有错误，请问应该怎么改