重复用户名验证 [英] dupicate username validation

问题描述

我创建了2页登录名和密码。我正在检查用户名的重复输入。

i已经为它编写了查询。但是如果用户名是相同的，如何阻止它插入.i已经尝试了进一步，但这是错误的。请帮助

这里是我的代码 -

i have created 2 pages login and password.and i am checking for duplicate entry of username.
i have written query for it.But how can prevent it from inserting if the username is same.i have tried further but it is wrong.pls help
here is my code-

 protected void signupbtn_Click(object sender, EventArgs e)
    {
        try
        {
            conn.Open();
        string st;
            st = "select count(username)from login where username='" + txtname.Text + "'";
            cmd = new SqlCommand(st, conn);
            if (st > 0)
            {
                Response.Write("duplicate record");
            }
         else
{
 cmd = new SqlCommand("insert into login(name,midname,surname,username,password,contact,dob,email,address,occupation,ltype) values('" + txtfirst.Text + "','" + txtmid.Text + "','" + txtsur.Text + "','" + txtname.Text + "','" + txtpass.Text + "','" + txtcontact.Text + "','" + txtdob.Text + "','" + txtemail.Text + "','" + txtaddr.Text + "','" + txtocc.Text + "','" + typeButtonList1.SelectedValue + "')", conn);


                cmd.ExecuteNonQuery();
                Response.Write("Record inserted");
            }
        }

推荐答案

注意 SQL_injection [ ^ ]因为在c＃中构建查询是不安全的..





尝试这样..

Be aware of SQL_injection[^] as it is not safe to frame the query in c#..


try like this..

conn.Open();
           string st;
           st = "select count(username)from login where username='" + txtname.Text + "'";
           var cmd = new SqlCommand(st, conn);
           DataTable dt = new DataTable();
           SqlDataAdapter da = new SqlDataAdapter(cmd);
           da.Fill(dt);
           int count = Convert.ToInt32(dt.Rows[0][0]);
           if (count >= 1)
           {
               Response.Write("duplicate record");
           }

首先，你听说过 SQL注入 [ ^ ]？应该以这样的方式创建ASP.NET应用程序，保护sql注入攻击 [< a href =http://msdn.microsoft.com/en-us/library/ff648339.aspxtarget =_ blanktitle =New Window> ^ ]。



我强烈建议使用存储过程并从后面的代码中调用它[< a href =http://support.microsoft.com/kb/306574/entarget =_ blanktitle =New Window> ^ ]。如果您想避免登录重复，请将此字段设置为唯一 [ ^ ]！

如何：创建和修改UNIQUE约束 [ ^ ]

First of all, have you ever heard about SQL injection[^]? An ASP.NET application should be created in that way which provide protection of sql injection attacks[^].

I strongly recommend to use stored procedures and call it from code behind[^]. If you would like to avoid logins duplication, set this field as unique[^]!
How to: Creating and Modifying UNIQUE Constraints[^]

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