How to call an event in one form from another?

[amitjaura]

My problem is that on button click of one form(Form1) I want to change the background color of checkbox in another form(Form2) ..One way I found is to call the form and pass the variable through constructor..Bt I don't want to create new form...The form in which I want 2 send the key is already opened n I don want to call the constructor.. Is it possible to call an event on form2 through the pressing of button on form 1....If yes then how?
*****I am working on windows application in C# .NET********

[balabaster]

There are a couple of ways you could do this...in the constructor of Form2 you could pass Form1 as a parameter...and hence you'd be able to access it's properties. Another way is to declare a public property in Form2 called parent which accepts the type Form and pass Form1 into it... again, you'd be able to call it's properties. The other way is with the use of singletons... I've never really found much use for singletons so I don't know all the ins and outs, but essentially it is this.

There is also a property "Parent" that will return a reference to the parent form (assuming you open Form2 as a child of Form1) - if not you can mimic this behaviour yourself easily enough:

Public Class Form1
 
  Private _Stuff As Boolean
  Public Property Stuff() As Boolean
    Get
      Return _Stuff
    End Get
    Set (ByVal Value As Boolean)
      _Stuff = value
      RaiseEvent ValueChanged(Me, New System.EventArgs)
    End Set
  End Property
 
  Public Event ValueChanged(ByVal Sender As Object, ByVal e As System.EventArgs)
 
  Public Sub Form2Loader()
 
    Dim oFrm2 As New Form2()
    oFrm2.Show(Me)
 
  End Sub
End Class

Form2 Class

Public Class Form2
 
    Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
 
        CType(Me.Owner, Form1).Stuff = CType(sender, CheckBox).Checked
 
    End Sub
 
End Class

[amitjaura]

There are a couple of ways you could do this...in the constructor of Form2 you could pass Form1 as a parameter...and hence you'd be able to access it's properties. Another way is to declare a public property in Form2 called parent which accepts the type Form and pass Form1 into it... again, you'd be able to call it's properties. The other way is with the use of singletons... I've never really found much use for singletons so I don't know all the ins and outs, but essentially it is this.

There is also a property "Parent" that will return a reference to the parent form (assuming you open Form2 as a child of Form1) - if not you can mimic this behaviour yourself easily enough:

Public Class Form1
 
  Private _Stuff As Boolean
  Public Property Stuff() As Boolean
    Get
      Return _Stuff
    End Get
    Set (ByVal Value As Boolean)
      _Stuff = value
      RaiseEvent ValueChanged(Me, New System.EventArgs)
    End Set
  End Property
 
  Public Event ValueChanged(ByVal Sender As Object, ByVal e As System.EventArgs)
 
  Public Sub Form2Loader()
 
    Dim oFrm2 As New Form2()
    oFrm2.Show(Me)
 
  End Sub
End Class

Form2 Class

Public Class Form2
 
    Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
 
        CType(Me.Owner, Form1).Stuff = CType(sender, CheckBox).Checked
 
    End Sub
 
End Class

Thank you sir,
Now I am trying to do this

[balabaster]

Thank you sir,
Now I am trying to do this

No problem, I hope it was useful...

[amitjaura]

No problem, I hope it was useful...

But one problem is coming I am using usercontrol as form1(in which I want to change the background color of checkbox) and System.Windows.Forms.Form as form 2(from which I want to raise an event of usercontrol(Form1)). Form1 and Form2 are not related to each other,means they are parent and child...
The coding you gave is related to the concept of parent and child...and it is not working ..I have tried a lot...
One thing I tried is I used a label in User Control(Form1) and I want to change the value of that label from Form2.Now in Form1 on the event LABLEVALURCHANGED I want to change the Background color of the checkbox.....To accomplish this task I want to assess the object of the Form1 which is opened at the instance...The main problem I am facing is that I am not able to find how to use that opened instance of the Form1

[jg007]

if I understand this is quite straightforward and I have given as really quick example below which just needs 2x forms 2x buttons on the first one and a checkbox on the second one

lol you can change the colour to whatever u want !

 
Public Class Form1
 
    Dim checkcol As System.Drawing.Color
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        checkcol = Color.Blue
        Form2.CheckBox1.BackColor = checkcol
        Form2.Show()
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        checkcol = Color.Chocolate
        Form2.CheckBox1.BackColor = checkcol
        Form2.Show()
 
    End Sub
End Class
 
 

[jg007]

just realised that this is c# the concepts may be similar but I have not got c# installed to check this.