Visual Studio 2012 Express 中的 C# 登录问题

伙计们，我正在一个项目中醒来，遇到了一些问题。它是一个写入本地数据库的基本登录应用程序。我知道在安全性方面这是不对的，但它仅用于概念验证。它在我的浏览器中验证并加载。然后，当我填写数据时，出现以下错误：

代码行突出显示：int temp = Convert.ToInt32(com.ExecuteScalar().ToString()); 错误如下：

SqlException 未由用户代码处理

"员工"附近的语法不正确

任何帮助不胜感激谢谢

这是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;
public partial class LoginPage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void btnLogin_Click(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ShowUsersConnectionString"].ConnectionString);
            conn.Open();
            string checkuser = "select count(*) form Staff where UserName='" + txtUserName.Text + "'";
            SqlCommand com = new SqlCommand(checkuser, conn);
            int temp = Convert.ToInt32(com.ExecuteScalar().ToString()); //
            conn.Close();

            if (temp == 1)
            {
                conn.Open();
                string CheckPassQuery = "select password from Staff where UserName='" + txtUserName.Text + "'";
                SqlCommand passcom = new SqlCommand(CheckPassQuery, conn);
                string password = passcom.ExecuteScalar().ToString();
                if (password == txtPassword.Text)
                {
                    Session["New"] = txtUserName.Text;
                    Response.Write("Password correct");
                    Response.Redirect("Users.aspx");
                }
                else
                {
                    Response.Write("Password is incorrect");
                }
            }
            else
            {
                Response.Write("Username ivalid");
            }
        }
    }
}

string checkuser = "select count(*) form Staff where UserName='" + txtUserName.Text + "'";