asp.net中 怎样进行用户名的唯一性检查.赠送100分.

Question

这是我的用户注册的代码，在userreg.aspx.cs 中,现在插入记录已经正常了，但我该怎样检测输入的用户名：username 和 数据表 theuser 中字段up_user 中的任何一条不同呢。（唯一性检查）。请高手们帮我插入一下那些代码。protected void Button1_Click(object sender, EventArgs e)
    {
            SqlConnection conn = new SqlConnection();
            ConnectionStringSettings s = ConfigurationManager.ConnectionStrings["upupSQLConnectionString"];
            String connString = s.ConnectionString;
            conn.ConnectionString = s.ConnectionString;
            
            String u_username = this.username.Text.ToString();
            String pass = this.password.Text.ToString();
            String textemail = this.email.Text.ToString();
            
            String sql = string.Format("insert into theuser(up_user,up_pass,up_email) values('{0}','{1}','{2}')", u_username, pass, textemail);
            System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql,conn);
            conn.Open();            command.ExecuteNonQuery();
            conn.Close();
            Response.Write("OK");
}

Answer 1

以username 为条件去查询数据库，看记录返回是否大于1

Answer 2

你先select一下看是否有这个记录

Answer 3

if exists(select [username] from [table_name] where [username]='user_name')

Answer 4

select count(*) from table1 where username='"+username+"'如果返回值大于0则存在记录..否则不存在记录

Answer 5

select count(username) from [table_name] where [username]='user_name'
判断这个值 是不是大于等于1

Answer 6

zhoufoxcn(执子之手) ( ) 信誉：100    Blog  2006-12-27 12:48:16  得分: 0  
 
 
   if exists(select [username] from [table_name] where [username]='user_name')
  
 
这个效率比count高

Answer 7

protected void Button1_Click(object sender, EventArgs e)
    {
            SqlConnection conn = new SqlConnection();
            ConnectionStringSettings s = ConfigurationManager.ConnectionStrings["upupSQLConnectionString"];
            String connString = s.ConnectionString;
            conn.ConnectionString = s.ConnectionString;
            
            String u_username = this.username.Text.ToString();
            String pass = this.password.Text.ToString();
            String textemail = this.email.Text.ToString();
            
   String sql = "if exists(select username from tablename where username ='"+user_name+" ')";
   
          sql += string.Format("insert into theuser(up_user,up_pass,up_email) values('{0}','{1}','{2}')", u_username, pass, textemail);
            System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql,conn);
            conn.Open();            command.ExecuteNonQuery();
            conn.Close();
            Response.Write("OK");
}

Answer 8

哪里有问题？  如果存在，则不执行下面的语句，应该怎样写呢？     String sql = "if exists(select up_user from theuser where up_user ='"+username+" ')";
    { 
       Response.Write("用户名已存在");
   Response.Redirect("userreg.aspx");
    }
       else
       {
           sql = string.Format("insert into theuser(up_user,up_pass,up_email) values('{0}','{1}','{2}')", u_username, pass, textemail);
            System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql,conn);
            conn.Open();            command.ExecuteNonQuery();
            conn.Close();
            Response.Write("OK");
}
   }

Answer 9

建唯一键在程序中不好判断是否重复,还是写代码检查较好
strsql="select count(*) from table1 where username='"+username+"'"
SqlCommand cmd=new SqlCommand(Session["chartsql"].ToString(),con);
cmd.CommandType=CommandType.Text;
SqlDataAdapter da=new SqlDataAdapter();
da.SelectCommand=cmd;
DataSet ds=new DataSet();
da.Fill(ds,"t");
if(ds.Tables["t"].Rows.Count>0)
{
Response.Write("该用户已存在");
}
这样就OK了!!

Answer 10

这个偶写过. 类似taobao那种，检测到有重复之后在页面给出提示信息!

Answer 11

设置一个主键，用出错页面提示用户 try ...    catch ....

Answer 12

这里我在数据库里设置usern为主键 确定唯一性  出现重复页面提示
  Dim usern As String = Trim(txt1.Text)
        Dim mima As String = Trim(txt2.Text)
        Dim sconstr As String = _
        System.Configuration.ConfigurationManager.AppSettings("scon")
        Dim con As SqlClient.SqlConnection = _
        New SqlClient.SqlConnection(sconstr)
        Dim sql As String = " insert into test(usern,mima) values(@usern,@mima) "
        Dim cmd As SqlClient.SqlCommand = _
        New SqlClient.SqlCommand(sql, con)
        con.Open()
        Try
            cmd.Parameters.Add(New SqlClient.SqlParameter("@usern", _
    SqlDbType.VarChar, 50)).Value = usern
            cmd.Parameters.Add(New SqlClient.SqlParameter("@mima", SqlDbType.VarChar, _
    50)).Value = mima
            cmd.ExecuteReader()
            lab2.Text = "注册成功"
        Catch ex As Exception
            lab2.Text = "帐号存在重复"
        End Try
        con.Close()

Answer 13

给你个SQL操作类 /// <summary> 
/// 检验是否存在数据 
/// </summary> 
/// <returns></returns> 
public bool ExistDate(string SQL) 
{ 
SqlConnection Conn; 
Conn = new SqlConnection(ConnStr); 
Conn.Open(); 
SqlDataReader Dr ; 
Dr = CreateCmd(SQL,Conn).ExecuteReader(); 
if (Dr.Read()) 
{ 
Dispose(Conn); 
return true; 
} 
else 
{ 
Dispose(Conn); 
return false; 
} 
}

Answer 14

现在代码没有出错，但好像不能正确判断。总是说”用户名被占用“ 应该怎样改？
同志们提供的代码我不知道怎么用进去。就在这上面改吧!谢谢了！
或者用IF ……ELSE ……行吗？ protected void Button1_Click(object sender, EventArgs e)
    {
            SqlConnection conn = new SqlConnection();
            ConnectionStringSettings s = ConfigurationManager.ConnectionStrings["upupSQLConnectionString"];
            String connString = s.ConnectionString;
            conn.ConnectionString = s.ConnectionString;
            
            String u_username = this.username.Text.ToString();
            String pass = this.password.Text.ToString();
            String textemail = this.email.Text.ToString();    
      
       try
       {
           String sql = "if exists(select up_user from theuser where up_user ='" + username + " ')";
          Response.Write("用户名被占用");
       }
       catch 
       {
           String sql = string.Format("insert into theuser(up_user,up_pass,up_email) values('{0}','{1}','{2}')", u_username, pass, textemail);
           System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql, conn);
           conn.Open();
           command.ExecuteNonQuery();
           Response.Write("注册成功"); 
       }
       conn.Close();
   
}

Answer 15

protected void Button1_Click(object sender, EventArgs e)
    {
            SqlConnection conn = new SqlConnection();
            ConnectionStringSettings s = ConfigurationManager.ConnectionStrings["upupSQLConnectionString"];
            String connString = s.ConnectionString;
            conn.ConnectionString = s.ConnectionString;
            
            String u_username = this.username.Text.ToString();
            String pass = this.password.Text.ToString();
            String textemail = this.email.Text.ToString();    
      
       try
       {
           String sql = "if exists(select up_user from theuser where up_user ='" + username + " ') begin select '用户名被占用' end else 
begin insert into theuser(up_user,up_pass,up_email)
values ('"+u_username+"', '"+pass+"', '"+textemail+"')
select '注册成功' 
end
"; System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql, conn);
           conn.Open();
           command.ExecuteNonQuery();                 }
       catch 
       {
          
   
           Response.Write("注册失败"); 
       }
       conn.Close();
   
}

Answer 16

protected void Button1_Click(object sender, EventArgs e)
    {
            SqlConnection conn = new SqlConnection();
            ConnectionStringSettings s = ConfigurationManager.ConnectionStrings["upupSQLConnectionString"];
            String connString = s.ConnectionString;
            conn.ConnectionString = s.ConnectionString;
            
            String u_username = this.username.Text.ToString();
            String pass = this.password.Text.ToString();
            String textemail = this.email.Text.ToString();
            
   String sql = "if exists(select username from tablename where username ='"+user_name+" ')";
   
          sql += string.Format("insert into theuser(up_user,up_pass,up_email) values('{0}','{1}','{2}')", u_username, pass, textemail);
            System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(sql,conn);
            conn.Open();            command.ExecuteNonQuery();
            conn.Close();
            Response.Write("OK");
}