Excel数据导入到DataGridView能显示，但是数据库没有更新，用Updata老是说无法找到tablemapping["teachingmaterial_info"！哪位高手帮忙看下啊！

 private DataSet ReadExcel(string strFileName, string sheetName)
        {            string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = " + strFileName + ";Extended Properties = Excel 8.0";
            OleDbConnection oleConnection = new OleDbConnection(strConnection);
            try
            {
                oleConnection.Open();
                DataSet dsRead = new DataSet();
                OleDbDataAdapter oleAdper = new OleDbDataAdapter(" SELECT * FROM [" + sheetName + "$]", oleConnection);
                oleAdper.Fill(dsRead);
                return dsRead;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
                return null;
            }
            finally
            {
                oleConnection.Close();
            }
        }private void 导入ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Hide();
            try
            {
                if (diaOpenFile.ShowDialog() == DialogResult.OK)
                {
                    if (diaOpenFile.OpenFile() != null)
                    {
                        LinkDataBase link = new LinkDataBase();
                        //ds = ReadExcel(@diaOpenFile.FileName, "Sheet1");
                        ds=link.UpdateDataBase(ReadExcel(@diaOpenFile.FileName, "Sheet1"), "teachingmaterial_info");
                        this.Visible = true;
                    }
                    else
                    {
                        this.Visible = true;
                    }
                }
            }
            catch (Exception Error)
            {
                MessageBox.Show("导入失败！" + Error.Message, "提示");
                this.Visible = true;
            }
        }public class LinkDataBase
    {
        private string strSQL;
        private string connectionString = "server=(local);database=TeachingMaterialManage;integrated security=sspi";
        private SqlConnection myConnection;
        private SqlCommandBuilder sqlCmdBld;
        private DataSet ds = new DataSet();
        private SqlDataAdapter da;
        public LinkDataBase() { }  //数据库更新(传DataSet和DataTable的对象)
        public DataSet UpdateDataBase(DataSet changedDataSet,string tableName)
        {
            this.myConnection = new SqlConnection(connectionString);
            this.da = new SqlDataAdapter(strSQL,myConnection);
            this.sqlCmdBld = new SqlCommandBuilder(da);
            this.da.Update(changedDataSet,tableName);
            return changedDataSet;
        }