c# - How to use while(datareader.Read()) -

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the following code throws exception after shows message box in if-else statement. exception says reader can't read, because closed:

try {     using (mysqlconnection conn = new mysqlconnection(config.connectionstring()))     {         conn.open();         mysqlcommand cmd = new mysqlcommand("select * tb_useraccounts;", conn);         mysqldatareader dr = cmd.executereader();          while (dr.read())         {             if (username == (dr["username"].tostring()) && password == (dr["password"].tostring()))             {                 frmmain main = new frmmain();                 main.show();                 login.hide();             }             else if (username == string.empty || password == string.empty)             {                 messagebox.show("please fill blank spaces!");             }             else             {                 messagebox.show("the username , password inserted incorrect!");             }             dr.close();             conn.close();         }     }

how can make while loop working properly?

you must close reader , connection after while loop bellow 

try    {    using (mysqlconnection conn = new mysqlconnection(config.connectionstring()))         {          conn.open();     mysqlcommand cmd = new mysqlcommand("select * tb_useraccounts;", conn);     mysqldatareader dr = cmd.executereader();       while (dr.read())      {         if (username == (dr["username"].tostring()) && password == (dr["password"].tostring()))                     {                         frmmain main = new frmmain();                         main.show();                         login.hide();                     }                     else if (username == string.empty || password == string.empty)                     {                         messagebox.show("please fill blank spaces!");                     }                     else                     {                         messagebox.show("the username , password inserted incorrect!");                     }                 }                     dr.close();                     conn.close();             }




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