数据库插入操作错误,是Datetime格式问题？

protected void BT_SubTz_Click(object sender, EventArgs e)
    {
        string title = TB_Title.Text.Trim();
        string words = TB_Words.Text.Trim();
        string companyname;
        string SQLstr;

        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["strConnection"].ConnectionString);     

        
        int type = Convert.ToInt32(DDL_Type.SelectedValue.ToString());
        if (type != 1)
        {
            TB_CompanyName.Visible = false;
            companyname = "指导员";
        }
        else
        {
            companyname = TB_CompanyName.Text.Trim();
        }

        SQLstr = "insert into tb_Content(subject,words,UserName,CreateTime,LastAnswerTime,HitCount,Type,CompanyName)"
                + "values('" + title + "','"
                + words + "',"
                + "'" + Session["UserName"].ToString() + "',"
                + DateTime.Now +","
                + DateTime.Now +","
                + "0," + type + ","
                + "'" + companyname + "')";
        SqlCommand myCmd = new SqlCommand(SQLstr, conn);       
        try
        {
            conn.Open();
            myCmd.ExecuteNonQuery();            
        }
        catch 
        {
            throw new Exception("连接服务器出错");
        }
        finally
        {
            myCmd.Dispose();
            conn.Close(); 
 
        }
    }

这是一个向数据库插入数据的函数，但是提示错误，不解，是因为DateTime插入格式的问题？ 数据库 DateTime
[解决办法]
使用DateTime.Now.ToString("yyyy-MM-ddTHH:mm:ss")