I want to make multiple mysql queries in the same time in C# -

i have code, when run select query works. when run insert query works. 2 queries can't work @ same time. don't know what's problem???! can me

public partial class signupfm : form     {         string str = @"server=localhost;database=bullivant_arabia_archive;userid=root;password='';";         mysqlconnection con = null;         mysqlcommand cmd = null;      public signupfm()     {         initializecomponent();     }      private void signupbt_click(object sender, eventargs e)     {          try         {             con = new mysqlconnection(str);             con.open();             if(checkuser(usernametb.text))             {                 if (password1tb.text == password2tb.text)                 {                     insertuser(this.usernametb.text, this.password1tb.text);                 }                 else                 {                     messagebox.show("you haven't enter same password twice");                 }             }             else             {                 messagebox.show("the user name exist, please enter one!");             }          }         catch (mysqlexception err)         {             console.writeline("error: " + err.tostring());         }                 {             if (con != null)             {                 con.close();             }         }     }      public void insertuser(string username, string password)     {         string userquery = @"insert login (username,password) values ('" + username + "' , '"                     + password + "')";         if (executeinsertquery(userquery))             messagebox.show("sign have been completed");         else             messagebox.show("sign couldn't completed");     }      bool checkuser (string username)     {         string query = @"select * login username = '" + username + "'";         if (executeselectquery(query))             return false;         else return true;     }      bool executeselectquery(string query)     {         cmd = new mysqlcommand(query, con);         if (cmd.executereader().read())             return true;         else return false;      }      bool executeinsertquery(string query)     {         cmd = new mysqlcommand(query, con);         if (cmd.executenonquery() == 1)             return true;         else return false;     } 

please share exact error getting. in opinion can't use same connection perform multiple queries. you'll fine using multiple connections, connection pooling works great mysql.