How do I execute code AFTER a form has loaded

Question

In  NET  Windows Forms have an event that fires before the Form is loaded  Form Load   but there is no corresponding event that is fired AFTER the form has loaded   I would like to execute some logic after the form has loaded   Can anyone advise on a solution

User · Accepted Answer

You could use the  Shown  event  MSDN - Form Shown   The Shown event is only raised the first time a form is displayed  subsequently minimizing  maximizing  restoring  hiding  showing  or invalidating and repainting will not raise this event

User · Answer

You could also try putting your code in the Activated event of the form  if you want it to occur  just when the form is activated   You would need to put in a boolean  has executed  check though if it is only supposed to run on the first activation

User · Answer

You can close your form after some execution      YourForm ActiveForm Close         LoadingForm ActiveForm Close

User · Answer

I sometimes use  in Load   this BeginInvoke  MethodInvoker  delegate        some code       or  this BeginInvoke  MethodInvoker  this SomeMethod      change  this  to your form variable if you are handling the event on an instance other than  this     This pushes the invoke onto the windows-forms loop  so it gets processed when the form is processing the message queue    updated on request   The Control Invoke Control BeginInvoke methods are intended for use with threading  and are a mechanism to push work onto the UI thread  Normally this is used by worker threads etc  Control Invoke does a synchronous call  where-as Control BeginInvoke does an asynchronous call   Normally  these would be used as   SomeCodeOrEventHandlerOnAWorkerThread          this code running on a worker thread      string newText   ExpensiveMethod       perhaps a DB web call       now ask the UI thread to update itself   this Invoke  MethodInvoker  delegate            this code runs on the UI thread        this Text   newText            It does this by pushing a message onto the windows message queue  the UI thread  at some point  de-queues the message  processes the delegate  and signals the worker that it completed    so far so good  -p  OK  so what happens if we use Control Invoke   Control BeginInvoke on the UI thread  It copes    if you call Control Invoke  it is sensible enough to know that blocking on the message queue would cause an immediate deadlock - so if you are already on the UI thread it simply runs the code immediately    so that doesn t help us     But Control BeginInvoke works differently  it always pushes work onto the queue  even it we are already on the UI thread  This makes a really simply way of saying  in a moment   but without the inconvenience of timers etc  which would still have to do the same thing anyway

User · Answer

I sometimes use  in Load   this BeginInvoke  MethodInvoker  delegate        some code       or  this BeginInvoke  MethodInvoker  this SomeMethod      change  this  to your form variable if you are handling the event on an instance other than  this     This pushes the invoke onto the windows-forms loop  so it gets processed when the form is processing the message queue    updated on request   The Control Invoke Control BeginInvoke methods are intended for use with threading  and are a mechanism to push work onto the UI thread  Normally this is used by worker threads etc  Control Invoke does a synchronous call  where-as Control BeginInvoke does an asynchronous call   Normally  these would be used as   SomeCodeOrEventHandlerOnAWorkerThread          this code running on a worker thread      string newText   ExpensiveMethod       perhaps a DB web call       now ask the UI thread to update itself   this Invoke  MethodInvoker  delegate            this code runs on the UI thread        this Text   newText            It does this by pushing a message onto the windows message queue  the UI thread  at some point  de-queues the message  processes the delegate  and signals the worker that it completed    so far so good  -p  OK  so what happens if we use Control Invoke   Control BeginInvoke on the UI thread  It copes    if you call Control Invoke  it is sensible enough to know that blocking on the message queue would cause an immediate deadlock - so if you are already on the UI thread it simply runs the code immediately    so that doesn t help us     But Control BeginInvoke works differently  it always pushes work onto the queue  even it we are already on the UI thread  This makes a really simply way of saying  in a moment   but without the inconvenience of timers etc  which would still have to do the same thing anyway

User · Answer

This an old question and depends more upon when you need to start your routines   Since no one wants a null reference exception it is always best to check for null first then use as needed  that alone may save you a lot of grief   The most common reason for this type of question is when a container or custom control type attempts to access properties initialized outside of a custom class where those properties have not yet been initialized thus potentially causing null values to populate and can even cause a null reference exceptions on object types  It means your class is running before it is fully initialized - before you have finished setting your properties etc  Another possible reason for this type of question is when to perform custom graphics   To best answer the question about when to start executing code following the form load event is to monitor the WM Paint message or hook directly in to the paint event itself  Why  The paint event only fires when all modules have fully loaded with respect to your form load event  Note  This visible    true is not always true when it is set true so it is not used at all for this purpose except to hide a form   The following is a complete example of how to start executing you code following the form load event  It is recommended that you do not unnecessarily tie up the paint message loop so we ll create an event that will start executing your code outside that loop   using System Windows Forms    namespace MyProgramStartingPlaceExample         lt summary gt      Main UI form object      lt  summary gt  public class Form1   Form             lt summary gt          Main form load event handler          lt  summary gt      public Form1                    Initialize ONLY  Setup your controls and form parameters here  Custom controls should wait for  FormReady  before starting up too          this Text    My Program title before form loaded              Size need to see text  lol         this Width   420              Setup the sub or fucntion that will handle your  start up  routine         this StartUpEvent    StartUPRoutine              Optional  Custom control simulation startup sequence             Define your class or control in variable  ie  var MyControlClass new CustomControl             Setup your parameters only  ie  CustomControl size   new size 420  966   Do not validate during initialization wait until  FormReady  is set to avoid possible null values etc              Inside your control or class have a property and assign it as bool FormReady - do not validate anything until it is true and you ll be good                   lt summary gt          The main entry point for the application which sets security permissions when set           lt  summary gt      static void Main                 Application EnableVisualStyles            Application SetCompatibleTextRenderingDefault false           Application Run new Form1                  region  WM Paint event hooking with StartUpEvent                            Create a delegate for our  StartUpEvent      public delegate void StartUpHandler                  Create our event handle  StartUpEvent      public event StartUpHandler StartUpEvent                Our FormReady will only be set once just he way we intendded        Since it is a global variable we can poll it else where as well to determine if we should begin code execution        bool FormReady                The WM Paint message handler  Used mostly to paint nice things to controls and screen     protected override void OnPaint PaintEventArgs e                   Check if Form is ready for our code           if  FormReady    false     Place a break point here to see the initialized version of the title on the form window                          We only want this to occur once for our purpose here              FormReady   true                                Fire the start up event which then will call our  StartUPRoutine  below              StartUpEvent                                    Always call base methods unless overriding the entire fucntion         base OnPaint e              endregion        region  Your StartUp event Entry point                Begin executuing your code here to validate properties etc  and to run your program  Enjoy         Entry point is just following the very first WM Paint message - an ideal starting place following form load     void StartUPRoutine                    Replace the initialized text with the following         this Text    Your Code has executed after the form s load event                         Anyway this is the momment when the form is fully loaded and ready to go - you can also use these methods for your classes to synchronize excecution using easy modifications yet here is a good starting point              Option  Set FormReady to your controls manulaly ie  CustomControl FormReady   true  or subscribe to the StartUpEvent event inside your class and use that as your entry point for validating and unleashing its code                        Many options  The rest is up to you             endregion

User · Answer

I sometimes use  in Load   this BeginInvoke  MethodInvoker  delegate        some code       or  this BeginInvoke  MethodInvoker  this SomeMethod      change  this  to your form variable if you are handling the event on an instance other than  this     This pushes the invoke onto the windows-forms loop  so it gets processed when the form is processing the message queue    updated on request   The Control Invoke Control BeginInvoke methods are intended for use with threading  and are a mechanism to push work onto the UI thread  Normally this is used by worker threads etc  Control Invoke does a synchronous call  where-as Control BeginInvoke does an asynchronous call   Normally  these would be used as   SomeCodeOrEventHandlerOnAWorkerThread          this code running on a worker thread      string newText   ExpensiveMethod       perhaps a DB web call       now ask the UI thread to update itself   this Invoke  MethodInvoker  delegate            this code runs on the UI thread        this Text   newText            It does this by pushing a message onto the windows message queue  the UI thread  at some point  de-queues the message  processes the delegate  and signals the worker that it completed    so far so good  -p  OK  so what happens if we use Control Invoke   Control BeginInvoke on the UI thread  It copes    if you call Control Invoke  it is sensible enough to know that blocking on the message queue would cause an immediate deadlock - so if you are already on the UI thread it simply runs the code immediately    so that doesn t help us     But Control BeginInvoke works differently  it always pushes work onto the queue  even it we are already on the UI thread  This makes a really simply way of saying  in a moment   but without the inconvenience of timers etc  which would still have to do the same thing anyway

User · Answer

First time it WILL NOT start  AfterLoading   It will just register it to start NEXT Load   private void Main Load object sender  System EventArgs e          Register it to Start in Load        Starting from the Next time      this Activated    AfterLoading     private void AfterLoading object sender  EventArgs e        this Activated -  AfterLoading        Write your code here

User · Answer

You could also try putting your code in the Activated event of the form  if you want it to occur  just when the form is activated   You would need to put in a boolean  has executed  check though if it is only supposed to run on the first activation

User · Answer

You can close your form after some execution      YourForm ActiveForm Close         LoadingForm ActiveForm Close

User · Answer

I know this is an old post  But here is how I have done it       public Form1 string myFile                InitializeComponent            this Show            if  myFile    null                        OpenFile myFile                        private void OpenFile string myFile   null                    MessageBox Show myFile

User · Answer

I sometimes use  in Load   this BeginInvoke  MethodInvoker  delegate        some code       or  this BeginInvoke  MethodInvoker  this SomeMethod      change  this  to your form variable if you are handling the event on an instance other than  this     This pushes the invoke onto the windows-forms loop  so it gets processed when the form is processing the message queue    updated on request   The Control Invoke Control BeginInvoke methods are intended for use with threading  and are a mechanism to push work onto the UI thread  Normally this is used by worker threads etc  Control Invoke does a synchronous call  where-as Control BeginInvoke does an asynchronous call   Normally  these would be used as   SomeCodeOrEventHandlerOnAWorkerThread          this code running on a worker thread      string newText   ExpensiveMethod       perhaps a DB web call       now ask the UI thread to update itself   this Invoke  MethodInvoker  delegate            this code runs on the UI thread        this Text   newText            It does this by pushing a message onto the windows message queue  the UI thread  at some point  de-queues the message  processes the delegate  and signals the worker that it completed    so far so good  -p  OK  so what happens if we use Control Invoke   Control BeginInvoke on the UI thread  It copes    if you call Control Invoke  it is sensible enough to know that blocking on the message queue would cause an immediate deadlock - so if you are already on the UI thread it simply runs the code immediately    so that doesn t help us     But Control BeginInvoke works differently  it always pushes work onto the queue  even it we are already on the UI thread  This makes a really simply way of saying  in a moment   but without the inconvenience of timers etc  which would still have to do the same thing anyway

User · Answer

I had the same problem  and solved it as follows   Actually I want to show Message and close it automatically after 2 second  For that I had to generate  dynamically  simple form and one label showing message  stop message for 1500 ms so user read it  And Close dynamically created form  Shown event occur After load event  So code is  Form MessageForm   new Form    MessageForm Shown     s  e1    gt         Thread t   new Thread      gt  Thread Sleep 1500         t Start         t Join         MessageForm Close

User · Answer

This an old question and depends more upon when you need to start your routines   Since no one wants a null reference exception it is always best to check for null first then use as needed  that alone may save you a lot of grief   The most common reason for this type of question is when a container or custom control type attempts to access properties initialized outside of a custom class where those properties have not yet been initialized thus potentially causing null values to populate and can even cause a null reference exceptions on object types  It means your class is running before it is fully initialized - before you have finished setting your properties etc  Another possible reason for this type of question is when to perform custom graphics   To best answer the question about when to start executing code following the form load event is to monitor the WM Paint message or hook directly in to the paint event itself  Why  The paint event only fires when all modules have fully loaded with respect to your form load event  Note  This visible    true is not always true when it is set true so it is not used at all for this purpose except to hide a form   The following is a complete example of how to start executing you code following the form load event  It is recommended that you do not unnecessarily tie up the paint message loop so we ll create an event that will start executing your code outside that loop   using System Windows Forms    namespace MyProgramStartingPlaceExample         lt summary gt      Main UI form object      lt  summary gt  public class Form1   Form             lt summary gt          Main form load event handler          lt  summary gt      public Form1                    Initialize ONLY  Setup your controls and form parameters here  Custom controls should wait for  FormReady  before starting up too          this Text    My Program title before form loaded              Size need to see text  lol         this Width   420              Setup the sub or fucntion that will handle your  start up  routine         this StartUpEvent    StartUPRoutine              Optional  Custom control simulation startup sequence             Define your class or control in variable  ie  var MyControlClass new CustomControl             Setup your parameters only  ie  CustomControl size   new size 420  966   Do not validate during initialization wait until  FormReady  is set to avoid possible null values etc              Inside your control or class have a property and assign it as bool FormReady - do not validate anything until it is true and you ll be good                   lt summary gt          The main entry point for the application which sets security permissions when set           lt  summary gt      static void Main                 Application EnableVisualStyles            Application SetCompatibleTextRenderingDefault false           Application Run new Form1                  region  WM Paint event hooking with StartUpEvent                            Create a delegate for our  StartUpEvent      public delegate void StartUpHandler                  Create our event handle  StartUpEvent      public event StartUpHandler StartUpEvent                Our FormReady will only be set once just he way we intendded        Since it is a global variable we can poll it else where as well to determine if we should begin code execution        bool FormReady                The WM Paint message handler  Used mostly to paint nice things to controls and screen     protected override void OnPaint PaintEventArgs e                   Check if Form is ready for our code           if  FormReady    false     Place a break point here to see the initialized version of the title on the form window                          We only want this to occur once for our purpose here              FormReady   true                                Fire the start up event which then will call our  StartUPRoutine  below              StartUpEvent                                    Always call base methods unless overriding the entire fucntion         base OnPaint e              endregion        region  Your StartUp event Entry point                Begin executuing your code here to validate properties etc  and to run your program  Enjoy         Entry point is just following the very first WM Paint message - an ideal starting place following form load     void StartUPRoutine                    Replace the initialized text with the following         this Text    Your Code has executed after the form s load event                         Anyway this is the momment when the form is fully loaded and ready to go - you can also use these methods for your classes to synchronize excecution using easy modifications yet here is a good starting point              Option  Set FormReady to your controls manulaly ie  CustomControl FormReady   true  or subscribe to the StartUpEvent event inside your class and use that as your entry point for validating and unleashing its code                        Many options  The rest is up to you             endregion

User · Answer

You could also try putting your code in the Activated event of the form  if you want it to occur  just when the form is activated   You would need to put in a boolean  has executed  check though if it is only supposed to run on the first activation

User · Answer

I had the same problem  and solved it as follows   Actually I want to show Message and close it automatically after 2 second  For that I had to generate  dynamically  simple form and one label showing message  stop message for 1500 ms so user read it  And Close dynamically created form  Shown event occur After load event  So code is  Form MessageForm   new Form    MessageForm Shown     s  e1    gt         Thread t   new Thread      gt  Thread Sleep 1500         t Start         t Join         MessageForm Close

User · Answer

First time it WILL NOT start  AfterLoading   It will just register it to start NEXT Load   private void Main Load object sender  System EventArgs e          Register it to Start in Load        Starting from the Next time      this Activated    AfterLoading     private void AfterLoading object sender  EventArgs e        this Activated -  AfterLoading        Write your code here

User · Answer

I know this is an old post  But here is how I have done it       public Form1 string myFile                InitializeComponent            this Show            if  myFile    null                        OpenFile myFile                        private void OpenFile string myFile   null                    MessageBox Show myFile

User · Answer

You could also try putting your code in the Activated event of the form  if you want it to occur  just when the form is activated   You would need to put in a boolean  has executed  check though if it is only supposed to run on the first activation

[c#] How do I execute code AFTER a form has loaded?

Examples related to c#

Examples related to .net

Examples related to winforms

Examples related to events