Excel中数据导入到SQL Server数据库

using System.Data.SqlClient;
using System.Data.OleDb;
  private void tsmiImportTeacherInfo_Click(object sender, EventArgs e)
        {
            DataSet ds;
            if (ofdImport.ShowDialog()==DialogResult.OK)
            {
                ds = ImportExcel(this.ofdImport.FileName);  //获得Excel
            }
            else
            {
                return;
            }
            int odr = 0;
            SqlConnection cn = db.sqlconnection();
            try
            {
                cn.Open();
                string str = "insert into Teacher (TeacherId,Pwd,eachCourse,TeacherName) values(@TeacherId,@Pwd,@TeachCourse,@TeacherName)";
                SqlCommand cmd = db.sqlcommand(str,cn);
                int dsLength = ds.Tables[0].Rows.Count;   //获得Excel中数据长度 
          &