mysql - Passing parameters by value -
to all, learning visual basic , working on windows application. have 2 text box methods (usernametextbox, passwordtextbox). in user enter data , hit submit button (button1_click). method call connect. want able do, have user type-in username , password. passed value, not reference connect() when invoked inside button method.
kind of authentication page. have values in connect(firstname:="johndoe", password:="password") - testing mysql server , demonstration of trying attempt.
imports mysql.data.mysqlclient public class securepasswordlist dim conn new mysqlconnection public sub connect(byval firstname string, byval password string) dim databasename string = "mysql" dim server string = "10.1.0.0" if not conn nothing conn.close() conn.connectionstring = string.format("server={0}; user id={1}; password={2}; database={3}; pooling=false", server, firstname, password, databasename) try conn.open() catch ex exception msgbox(ex.message) end try conn.close() end sub private sub button1_click(sender object, e eventargs) handles button1.click connect(firstname:="johndoe", password:="password") end sub private sub securepasswordlist_load(sender object, e eventargs) handles mybase.load end sub private sub usernametextbox_textchanged(sender object, e eventargs) handles usernametextbox.textchanged dim firstname string firstname = usernametextbox.text end sub private sub passwordtextbox_textchanged(sender object, e eventargs) handles passwordtextbox.textchanged dim password string password = passwordtextbox.text end sub end class
change
private sub button1_click(sender object, e eventargs) handles button1.click connect(firstname:="johndoe", password:="password") end sub to
private sub button1_click(sender object, e eventargs) handles button1.click connect(firstname, password) end sub but should ensure firstname , password initialized , held class variables. move
dim firstname string dim firstname string to in class, not event handling functions (click etc). this:
public class securepasswordlist dim conn new mysqlconnection dim firstname string dim firstname string but can redo code (as want text controls):
imports mysql.data.mysqlclient public class securepasswordlist dim conn new mysqlconnection public sub connect(byval firstname string, byval password string) dim databasename string = "mysql" dim server string = "10.1.0.0" if not conn nothing conn.close() conn.connectionstring = string.format("server={0}; user id={1}; password={2}; database={3}; pooling=false", server, firstname, password, databasename) try conn.open() catch ex exception msgbox(ex.message) end try conn.close() end sub private sub button1_click(sender object, e eventargs) handles button1.click connect(usernametextbox.text, passwordtextbox.text) end sub end class i dont think passing value or reference issue here. want connect function modify strings passed it? doubt it. in case value or reference fine. strings passed copied instance reference, in effect passed value unless use byref in function declaration will. every class (int, string, etc) passed differently in vb default. need check each type know if specify byval or byref. string creates copy of string if use byval, accessed using pointer newly created string. depends how deep want dig too
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