创建EventHandler并从另一个类监听Event

Question

I've created event as bellow and want to listen to it and execute method in another class when it fires but saveEvent always comes to be null and it doesn't fire I don't know what I've missed

here's my first class has button

internal partial class OpenSaveReportWizardForm : Form
{
public event EventHandler saveEvent;
private void saveButton_Click(object sender, EventArgs e)
{
  saveEvent?.Invoke(this, e); 
}
}

and here's the second class where I want to listen to saveEvent

 internal class Database
 {
  public Database()
  { 
        Program._wizardForm.saveEvent += (sender, e) => HandleSaveMethod( );

  }

public void HandleSaveMethod()
  {
   // do something
  }

here's where I open the form

internal  class Program
{
  public static OpenSaveReportWizardForm _wizardForm;
  private static void Main()
  {
  OpenFileCommandHandler();
  }

void OpenFileCommandHandler()
     { 
        _wizardForm = new OpenSaveReportWizardForm( );

        _wizardForm.ShowDialog(); 
     }
 }

Answer 1

Because you disposed wizardForm, after that event is cleared. You should write next code:

 internal class Database
 {
    private bool _isDisposed;
    private OpenSaveReportWizardForm _wizardForm;

  public Database()
  {
      _wizardForm = new  OpenSaveReportWizardForm(m_Opening,m_ConnectionProperties,m_ColumnProperties))
      _wizardForm.saveEvent += (sender, e) => HandleSaveMethod( );

  }

public void HandleSaveMethod()
  {
   // do something
  }

  public void Dispose()
  {
    if(_isDisposed)
        return;

    _isDisposed = true;

    _wizardForm.saveEvent -= HandleSaveMethod;
    _wizardForm.Dispose();
  }