how to remove/deactive a handler from an event (Textbox Changed) from Winform using VB.NET running on Visual Studio 2019

Question

how to remove/deactive a handler from an event (Textbox Changed) from Winform using VB.NET running on Visual Studio 2019

Josh S 26

Hi,
First of all I want to say thank you and my sincere gratitude this community, for monumental help and support you all are providing to the Developer/Engineer/Scientist communities across the Globe.
I am facing a huge challenge that involve a Textbox Text Changed event. So here you go.

I have a WinForms application that is running on Windows 10 environment. Multiples copy on the same form running at the same time on different Windows Console. At least minimum two forms can run at any time and maximum fifteen forms.

A person can select a specific sailboat lets say its SailBoatA on a console and select a button "Details", which open the SailBoatDetails form. This provides details about the sailboatA.
Another console someone could select another sailboat - SailBoatB and select details button, which open for SailBoatB - SailBoatDetails form.

SailBoatDetails form has following two text boxes:
**Destination Distance:
Arriving Port:****

On SailBoatDetails form for SailBoatA, an user could enter value 1100 in "Destination Distance" text box.
Then user will select an Apply button on the form and this value will be saved on a table. The enter value still displayed on the text box.

However on another console SailBoatB "Destination Distance" text box displayed the same value. Which should not.
I debugged and observed that in another console for SailBoatB

Private Sub txtDestinationDistance_TextChanged(sender As Object, e As EventArgs) Handles txtDestinationDistance.TextChanged
sub gets activated.

Sender object has the 1100.

How I can stop textbox change events after a user select "Apply" button for "SailBoatA"?
So I can prevent this event to go any other console?

Here is the code for the text box

Private Sub txtDestinationDistance_TextChanged(sender As Object, e As EventArgs) Handles txtDestinationDistance.TextChanged

    Dim thisBoat As SpecialBoatA = AllBoats.HookAnyBoat

    If thisBoat IsNot Nothing Then
        thisBoat.distance = txtDestinationDistance.Text

        ...
    ...

    Else

        txtDestinationDistance.Text = ""
    End If

End Sub

Viorel 122.6K Reputation points

2021-12-13T10:02:23.08+00:00

Maybe the Apply button does not work well?
Josh S 26 Reputation points

2021-12-14T06:38:30.477+00:00

please explain what do you mean ?

Here's my code

Private Sub Apply_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Apply.Click

'Some other codes
Save_Data(thisBoat)

End Sub
Viorel 122.6K Reputation points

2021-12-14T06:42:36.697+00:00

Maybe the problem is caused by 'Some other codes' or Save_Data, or by the value of thisBoat. Do you observe the same problem if you temporarily comment the code or some parts of Apply_Click?
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-14T08:49:42.037+00:00

Hi @Josh S ,
When does SailBoatB "Destination Distance" text box displayed the same value as SailBoatA?
Before or after the Apply button clicked?
Josh S 26 Reputation points

2021-12-15T05:19:27.4+00:00

After the "Apply" button clicked.
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-15T07:49:01.313+00:00

Hi @Josh S ,
So as Viorel-1 said, maybe the problem is caused by'Some other codes' or Save_Data, or by the value of thisBoat.
Could you please provide more information about the above mentioned conten?
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-23T08:14:52.46+00:00

Hi @Josh S ,
May I know if you have got any chance to check my reply?
Whether your issue has been solved or not?
If not, it will be great if you can share more detailed information for us to better investigate this issue.
Thanks for your cooperation.

3 answers

Your answer

Viorel 122.6K Reputation points

2021-12-13T10:02:23.08+00:00

Maybe the Apply button does not work well?
Josh S 26 Reputation points

2021-12-14T06:38:30.477+00:00

please explain what do you mean ?

Here's my code

Private Sub Apply_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Apply.Click

'Some other codes
Save_Data(thisBoat)

End Sub
Viorel 122.6K Reputation points

2021-12-14T06:42:36.697+00:00

Maybe the problem is caused by 'Some other codes' or Save_Data, or by the value of thisBoat. Do you observe the same problem if you temporarily comment the code or some parts of Apply_Click?
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-14T08:49:42.037+00:00

Hi @Josh S ,
When does SailBoatB "Destination Distance" text box displayed the same value as SailBoatA?
Before or after the Apply button clicked?
Josh S 26 Reputation points

2021-12-15T05:19:27.4+00:00

After the "Apply" button clicked.
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-15T07:49:01.313+00:00

Hi @Josh S ,
So as Viorel-1 said, maybe the problem is caused by'Some other codes' or Save_Data, or by the value of thisBoat.
Could you please provide more information about the above mentioned conten?
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2021-12-23T08:14:52.46+00:00

Hi @Josh S ,
May I know if you have got any chance to check my reply?
Whether your issue has been solved or not?
If not, it will be great if you can share more detailed information for us to better investigate this issue.
Thanks for your cooperation.

Answer 1

Karen Payne MVP 35,586 Volunteer Moderator

Rather than use Handles txtDestinationDistance.TextChanged, use AddHandler and RemoveHandler and eliminate using Handles

Example, type Karen or karen or KAREN and insert Payne

Public Class Form1  
    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs)  
  
        If String.Equals(TextBox1.Text, "karen", StringComparison.OrdinalIgnoreCase) Then  
            RemoveHandler TextBox1.TextChanged, AddressOf TextBox1_TextChanged  
            TextBox1.Text = "Karen Payne"  
            TextBox1.SelectionStart = TextBox1.Text.Length  
            TextBox1.SelectionLength = 0  
            AddHandler TextBox1.TextChanged, AddressOf TextBox1_TextChanged  
        End If  
  
    End Sub  
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
        AddHandler TextBox1.TextChanged, AddressOf TextBox1_TextChanged  
    End Sub  
End Class

Josh S 26 Reputation points

2021-12-13T16:10:50.103+00:00

Hi Thank you,

Could you please give me an example.
Karen Payne MVP 35,586 Reputation points Volunteer Moderator

2021-12-13T17:07:47.09+00:00

See my updated answer for an example.

Answer 2

Hi,
Countless gratitude for this code sample and implemented in my code, here is the sample

Private Sub ShipDetails_Load(sender As Object, e As EventArgs) Handles MyBase.Load
....
....
AddHandler txtDestinationDistance.TextChanged, AddressOf txtDestinationDistance_TextChanged
End Sub

Private Sub txtDestinationDistance_TextChanged(sender As Object, e As EventArgs)

    Dim thisBoat As SpecialBoatA = AllBoats.HookAnyBoat

    If thisBoat IsNot Nothing Then
    'First I try to add the following line in this part of the code. 
    'RemoveHandler txtDestinationDistance.TextChanged, AddressOf txtDestinationDistance_TextChanged

        thisBoat.distance = txtDestinationDistance.Text

        ...
    ...

    Else

        txtDestinationDistance.Text = ""
    End If
'Then I commented out the line from "IF..then" part and add the following line. 
    RemoveHandler txtDestinationDistance.TextChanged, AddressOf txtDestinationDistance_TextChanged

End Sub

Private Sub Apply_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Apply.Click

'Some other codes
Save_Data(thisBoat)

RemoveHandler txtDestinationDistance.TextChanged, AddressOf txtDestinationDistance_TextChanged

End Sub

I still have the same issue, another console SailBoatB "Destination Distance" text box displayed the same value that I entered for
SailBoatA in a different console .

I debugged and observed that for SailBoatB, sender object displayed the value I entered for SailBoatA.

Also I added "RemoveHandler txtDestinationDistance.TextChanged..." line in "Apply" push button code, towards the end after entered text value is saved. This is test, if this will stop the issue but it didn't.

Please enlighten me, thank you.

Answer 3

Josh S 26

I am curious if this issue could be stop using an event. I am not familiar with Event and Event handler.

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how to remove/deactive a handler from an event (Textbox Changed) from Winform using VB.NET running on Visual Studio 2019

3 answers

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