c# - I want to check the username is already exists in my database table or not? -

i have registration page , want check username exist in database or not in 3 tier architecture.

myregistration.cs:

public static int checkusername(string user_txt)  {   int id2 = 0;   string selectstr = "select * xyz username = '" + user_txt + " ' ";   id2 = dataaccesslayer.executereader(selectstr);   return id2;      } 

and code behind onclick event of textbox:

protected void txt_username_textchanged(object sender, eventargs e)  {   if (!string.isnullorempty(txt_username.text))    {     int id = xyz.checkusername(txt_username.text.trim());     if (id > 0)      {       lblstatus.text = "username taken";      }     else      {       lblstatus.text = "username available";      }    }    } 

dataaccesslayer:

public static int executereader(string query)  {   sqlconnection con = new sqlconnection();   con.connectionstring = getconnectionstring();   con.open();   int id = 0;               sqlcommand cmd = new sqlcommand();   cmd.commandtext = query;   cmd.commandtype = system.data.commandtype.text;   cmd.connection = con;   sqldatareader reader = cmd.executereader();   while (reader.read())    {     id++;    }   cmd = null;   reader.close();   con.close();   return id;  } 

i have edited of codes try below... you...

text change event :

    protected void txt_username_textchanged(object sender, eventargs e)     {         if (!string.isnullorempty(txt_username.text))         {             if (xyz.checkusername(txt_username.text.trim()))             {                 lblstatus.text = "username taken";             }             else             {                 lblstatus.text = "username available";             }         }      } 

check username :

    public bool checkusername(string user_txt)     {         bool result;         result = dataaccesslayer.executereader(user_txt);         return result;     } 

excute reader :

    public bool executereader(string user_txt)     {         sqlconnection con = new sqlconnection();         con.connectionstring = getconnectionstring();         con.open();         sqlcommand cmd = new sqlcommand("select * xyz username = @userid", con);         sqlparameter param = new sqlparameter();         param.parametername = "@userid";         param.value = user_txt;         cmd.parameters.add(param);         sqldatareader reader = cmd.executereader();         if (reader.hasrows)             return true;         else             return false;     }