我尝试使用mysql在visual studio 2017 asp.net c#web应用程序中登录页面，结果显示以下错误：
第33行：querystr=“select*from webapp.userregistration where username='”+usernametextbox.text+“'and password='”+passwordtexbox.text；第34行：cmd=new mysql.data.mysqlclient.mysqlcommand（querystr，conn）；第35行：reader=cmd.executereader（）；第36行：第37行：name=“”；
源文件：c:\users\home\source\repos\webpage\webpage\default.aspx.cs行：35
堆栈跟踪：
[mysqlexception（0x80004005）：您的sql语法有错误；在第1行，检查与mysql服务器版本相对应的手册中的正确语法]
mysql.data.mysqlclient.mysqlstream.readpacket（）+309
mysql.data.mysqlclient.nativedriver.getresult（int32&affectedrow，int64&insertedid）+67
mysql.data.mysqlclient.driver.getresult（int32 statementid，int32&affectedrows，int64&insertedid）+17
mysql.data.mysqlclient.driver.nextresult（int32 statementid，boolean force）+110 mysql.data.mysqlclient.mysqldatareader.nextresult（）+875 mysql.data.mysqlclient.mysqlcommand.executereader（commandbehavior）+1688 mysql.data.mysqlclient.mysqlcommand.executereader（）+6网页。\u默认值。提交\u单击（object sender，eventargs e）在c:\users\home\source\repos\webpage\webpage\default.aspx.cs:35中
system.web.ui.webcontrols.button.onclick（eventargs e）+9782450
system.web.ui.webcontrols.button.raisepostbackevent（string eventargument）+204
system.web.ui.webcontrols.button.system.web.ui.ipostbackeventhandler.raisepostbackevent（string eventargument）+12
system.web.ui.page.raisepostbackevent（ipostbackeventhandler sourcecontrol，string eventargument）+15
system.web.ui.page.raisepostbackevent（namevaluecollection postdata）+35 system.web.ui.page.processrequestmain（布尔includestagesbeforeasyncpoint，布尔includeStagesSafterAsyncPoint）+1639
代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System;
using System.Data;

using MySql.Data;
using MySql.Data.MySqlClient;

namespace WebPage
{
    public partial class _default : System.Web.UI.Page
    {
        MySql.Data.MySqlClient.MySqlConnection conn;
        MySql.Data.MySqlClient.MySqlCommand cmd;
        MySql.Data.MySqlClient.MySqlDataReader reader;
        String name;
        protected void Page_Load(object sender, EventArgs e)
        {
            DoSQLQuery();
        }

        protected void Submit_Click(object sender, EventArgs e)
        {

            String connString = System.Configuration.ConfigurationManager.ConnectionStrings["WebAppConnString"].ToString();
            conn = new MySql.Data.MySqlClient.MySqlConnection(connString);
            conn.Open();
            String queryStr = "";
             queryStr = "SELECT * FROM webapp.userregistration WHERE username='" + usernameTextBox.Text+ "'AND password='" + passwordTextBox.Text;
            cmd = new MySql.Data.MySqlClient.MySqlCommand(queryStr,conn);
            reader = cmd.ExecuteReader();

            name = "";
            while (reader.HasRows && reader.Read())
            {

                {
                    name = reader.GetString(reader.GetOrdinal("username")) + " " + reader.GetString(reader.GetOrdinal("password"));
                }

                //if the data matches the rows (username, password), then you enter to the page
                if (reader.HasRows)
                {
                    Session["uname"] = name;

                    Response.BufferOutput = true;
                    Response.Redirect("login.aspx", false);

                }
                else
                {
                    passwordTextBox.Text = "invalid user";

                }
            }

            reader.Close();
            conn.Close();
        }

        private void DoSQLQuery()
        {
            try
            {

            }
            catch (Exception e)
            {
                passwordTextBox.Text = e.ToString();
            }
        }
    }
}