How to pass a parameter to another class using events

问题

I have a usercontrol which is having one button

Usercontrolclass.cs

Button click event

  private void btn_OK_Click(object sender, EventArgs e)
        {
            value= Convert.ToDouble(txt_ActualValue.Text);

            if(getvalue!=null)
            getvalue(null, new EventArga());
        }

private variable

private int value;

property:

 public double finalvalue
        {
            get
            {
                return value;
            }
        }

MainForm.cs

I'm using that Usercontrol into this mainform

I need to get the value from this class

in constructor:

Usercontrolclass.getvalue+=Usercontrolclass_getvalue;

in method:

 private void   UserControlclass_getvalue()
    {
      here I need to get the "value";

     int myval = Usercontrolclass.finalvalue;  // I can get like this
    }

my question is without using properties simply pass a parameter into the event arguments and get the value in to the mainfrom?

  if(getvalue!=null)
                getvalue(null, new EventArga(value));

Because I don't allowed to do like this classname.properties

as well as don't allowed to pass a parameter using method like this

in Usercontrol class

 Mainform obj = new Mainform ();
            obj.getvalue(value);

Is there any other way to do this? I mean pass a variable to another class by using events?

回答1:

You can make your own events, you can fire them from the usercontrol (here is where the event takes place) and put a listener on your main form.

User control:

//You custom event, has to be inside namespace but outside class
public delegate void MyCustomEvent(int value);

public partial class aUserControl : UserControl
{
    //Here you initialize it
    public event MyCustomEvent CustomEvent;

    public aUserControl()
    {
        InitializeComponent();
    }

    private void theButton_Click( object sender, EventArgs e )
    {
        CustomEvent?.Invoke(5);//using magic number for test
        //You can call this anywhere in the user control to fire the event
    }
}

Now in the main form I added the usercontrol and an event listener

Main form:

public Form1()
{
    InitializeComponent();

    //Here you add the event listener to your user control
    aUserControl1.CustomEvent += AUserControl1_CustomEvent;
}

private void AUserControl1_CustomEvent( int value )
{
    MessageBox.Show(value.ToString());
    //This is the Main form and I now have the value here 
    //whenever the button is clicked (or event is fired from somewhere else)
}

来源：https://stackoverflow.com/questions/45182850/how-to-pass-a-parameter-to-another-class-using-events

标签

events

parameters

delegates