如何在注册页面上防止重复用户？ [英] How to prevent duplicate user on signup page ?

问题描述

我有2页登录和注册。我想检查用户是否已经存在。



我尝试过：

i have 2 pages login and signup. and I want to check whether the user is already exist or not.

What I have tried:

//this is my code in registration form

public partial class Login : System.Web.UI.Page
{
    string cs = ConfigurationManager.ConnectionStrings["NDBCS"].ConnectionString;
    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
            LoadTrack();
        }

        
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection(cs);
        con.Open();
        SqlCommand cmd = new SqlCommand("Insert into tbl_User (Firstname, Lastname, Track_id, Username, Email, Password) values (@firstname, @lastname, @track, @username, @email, @password)", con);
        cmd.Parameters.AddWithValue("@firstname", txtbox_FN.Text);
        cmd.Parameters.AddWithValue("@lastname", txtbox_LN.Text);
        cmd.Parameters.AddWithValue("@track", ddl_Track.SelectedValue);
        cmd.Parameters.AddWithValue("@username", txtbox_UN.Text);
        cmd.Parameters.AddWithValue("@email", txtbox_Email.Text);
        cmd.Parameters.AddWithValue("@password", txtbox_PW.Text);
        cmd.ExecuteNonQuery();
        con.Close();
    }

    private void LoadTrack()
    {
        try
        {
            using (SqlConnection con = new SqlConnection(cs))
            {
                SqlCommand cmd = new SqlCommand("select * from tbl_Track", con);
                con.Open();
                DataTable table = new DataTable();
                SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                adapter.Fill(table);

                ddl_Track.DataSource = table;
                ddl_Track.DataValueField = "Track_id";
                ddl_Track.DataTextField = "Track_code";
                ddl_Track.DataBind();
                ddl_Track.Items.Insert(0, new ListItem("--Select Category--", "0"));
            }
        }

        catch (Exception ex)
        {

            Label1.ForeColor = System.Drawing.Color.Red;
            Label1.Text = "Something went wrong!." + ex.Message + "";
            Label1.Visible = false;
        }
    }

推荐答案

检查电子邮件：添加 SQL UNIQUE Con​​straint [ ^ ]到列（并使用 try ... catch 块来处理现有用户）或首先执行SELECT，然后查看是否在那。

我？我会做两个......



但更重要的是，不要这样做： CodeCrime：基于文本的密码 [ ^ ]

请参阅：密码存储：如何操作。 [ ^ ]

Check the email: Either add a SQL UNIQUE Constraint[^] to the column (and use a try...catch block to handle existing users) or do a SELECT first, and see if it's there.
Me? I'd do both...

But more importantly, don't do it like that: CodeCrime: text based passwords[^]
See here: Password Storage: How to do it.[^]

简单检查用户名和电子邮件是否已经退出数据库..

Simple you check UserName And Email already exits or not in your Database ..

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