How to Detect Textbox Change

[Lee.B]

The Textbox_TextChanged event fires when a key is pressed or when text is pasted while cursor is in a text box.

Is there an event that fires on Textbox1.text="NewText"? How do I detect this?

My reason for doing this is I would like to reformat text property automatically on assignment rather than do something like textbox.text=myreformat("Newtext")

I can put code in validating or validated event but then I'd have to force focus/lostfocus to trigger one of those events.

Any suggestions?

Lee

[Mr.Joker]

Just make a statement:

If TextBox1.Text = "New Text" Then 
'Code to do
End If

[Lee.B]

Need to do this as a textbox Event.
Also, forgot to mention that I can't use the TextChanged event cuz that fires on every key stroke.
Need an event that fires on assignment.

LB

[Mr.Joker]

It shouldnt run everytime. The code I gived you above will be executed only and only if textbox text have New Text writen inside. If it doesent it will never run. I can type forever then. Just double click on textbox and try this:

If TextBox1.Text = "New Text" Then
            MessageBox.Show("You typed New Text in TextBox")
        End If

Then , you run application and type New Text. Only then event will run,

[Lee.B]

Joker:
Yes, that does work if I know what user is assigning to Text property.
I do not know what user will be entering as it could be a decimal variable, a date or maybe just text.
I need this event to format entry for display.
So, for example if a number is assigned, I might want to format it as currency before displaying it or if a date is assigned, format date as Long Date.

lb

[Mr.Joker]

If you tell me what excatly you want, and not examples I can give you the code. I cant type a code if you dont tell me what you really want to do. Just say "I want you give me a code that will make a number from textbox into text, or whatever". Ok?

[chipp]

- if the textbox.text changed because of the user's input then we can check it using "TextChanged" method
- if the text changed by the code, the you're the one who decide the next step, for example:

if textbox1.Text = "something" Then
    '...
End If

[thebuffalo]

Try making the event TextBox_Leave, so when you click out of the textbox it will run the code.

[Lee.B]

OK - Lets try this.
Place 2 text boxes on a form and also a button.
Add my code to the form.

Enter 123 in textbox1 and press tab or click on textbox2 to terminate input.
Notice that textbox1 has been reformatted to display currency $123.00

Now, enter 456 in textbox2 and click button to set textbox1.text=textbox2.text

Notice that textbox1 now shows 456 not $456.00 as I want.

Must somehow have an event that responds to the assignment that executes the following:
TextBox1.Text = Convert.ToDecimal(Decimal.Parse(TextBox1.Text, Globalization.NumberStyles.Currency)).ToString("c")

Public Class Form2

    Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim DecSep As String = Globalization.CultureInfo.CurrentCulture.NumberFormat.CurrencyDecimalSeparator

        If e.KeyChar = Chr(8) Then
            Exit Sub
        ElseIf Char.IsNumber(e.KeyChar) = False Then
            If e.KeyChar = DecSep Then
                Exit Sub
            Else
                e.Handled = True
                Exit Sub
            End If
        End If
    End Sub


    Private Sub TextBox1_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
        Dim currency As Decimal
        'Convert the current value to currency, with or without a currency symbol.
        If Not Decimal.TryParse(TextBox1.Text, _
                                Globalization.NumberStyles.Currency, _
                                Nothing, _
                                currency) Then
            'Don't let the user leave the field if the value is invalid.
            With TextBox1
                .HideSelection = False
                .SelectAll()
                MessageBox.Show("Please enter a valid currency amount.", _
                                "Invalid Value", _
                                MessageBoxButtons.OK, _
                                MessageBoxIcon.Error)
                .HideSelection = True
            End With
            e.Cancel = True
        End If
    End Sub

    Private Sub TextBox1_Validated(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.Validated
        'Display the value as local currency.
        TextBox1.Text = Convert.ToDecimal(Decimal.Parse(TextBox1.Text, Globalization.NumberStyles.Currency)).ToString("c")
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.Text = TextBox2.Text
    End Sub
End Class

[Shaggy Hiker]

Yeah, that's not going to happen...at least not automatically. The control knows when the text has changed, but it can't know HOW the text was changed. That would require the control to know about things beyond the object itself. I suppose it would be possible if the = operator was overloaded for the control such that it raised a different event when that operator was used, but I'm not sure that even that would work (after all, there has to be assignment somewhere in there whenever you type text into a control, and the operator would be overloaded for the contol, not just a property of the control). In any case, the operator isn't overloaded, so that's not an option.

However, you can make your own event if you want to. whenever you assign to the textbox in code, raise the event. That's pretty much all you can do, because what you are really asking for is not nearly as distinct as you seem to think it is. You already have the event for TextChanged, and you already know the limitations of that event, but it is the only event possible. After all, when you are typing into a textbox, each character is coming in at any one time. Nobody types fast enough for those characters to appear as anything other than slow, character by character, entries. Pure tedium for the computer. Therefore, the computer can't really know when you are done entering text, which is why the validating and Leave and LostFocus events exist. The case you are looking at is when text is changed, but changed in a certain way, which may or may not be distinct.

There are two things you might consider trying:

1) Cache the value in the textbox. In the textChanged event, compare the new to the old. If the difference in the length is anything other than 1, do the formatting then. This would pick up most of the cases, but will fail noticeably in several situations (e.g. the textbox has 123.45 and you assign 123.456). You might try comparing the text between the two, but as you can see in that example, there is no way to distinguish between typing entry and assignment between those two.

2) Watch the KeyDown event as well as TextChanged. If you get TextChanged without KeyDown, then entry was either by assignment or by copy and paste. If you get KeyDown AND TextChanged, then the entry was by typing. That may be a good enough distinction for your purposes. It may fail, also. I'm not sure whether Ctrl+P pasting would cause the KeyDown (it probably would), but you can exlcude that by checking the key combination.

It's not all that easy, but the key point is that you have to be able to determine what is distinct about assignment vs typing. There isn't much that is distinct, but if you play around with it, there might be just barely enough to work with.

[.paul.]

2\ alternatively, inherit the textbox + override the wndProc + capture the WM_PASTE message, along with overriding the onTextChanged event to test keyboard input

[Lee.B]

Paul:
Don't understand a thing you said . How about a code example?

On another note.... I see you're from Chelmsford - I had some friends that lived there in an old priory back in the 60's. I used to go there to visit them when I lived in London.

Lee
(Florida - USA)

[.paul.]

ok. where's the priory?

try this. add the class to your project. after rebuilding, you'll find the observableTextBox control at the top of your toolbox + you add it like any control:

Public Class observableTextBox
    Inherits TextBox
 
    Const WM_PASTE As Integer = &H302
 
    Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)
        MsgBox("KeyPress")
        MyBase.OnKeyPress(e)
    End Sub
 
    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        If m.Msg = WM_PASTE Then
            MsgBox("Paste")
        End If
        MyBase.WndProc(m)
    End Sub
 
End Class

[Lee.B]

Paul:
Thank you for the code example - however, it still does not identify an assignment. Paste or Keypress require that cursor is in the textbox and a subsequent "Validate" event is available to trigger the code required to reformat the displayed text. Validate is not fired on assignment unfortunately. Guess I'll just put formatting in a function and use textbox.text=myFormat(value) when I do an assignment.

As far as the Priory, as I remember it was a house in town (short walk to pub) built in 17th century.
It had a ceiling with exposed arched beams in reception area with minstrel gallery. Also I remember a huge fireplace in kitchen and wood paneled walls in the sleeping rooms. I seem to remember it was on Chelmsford Road or Bridge Street but that was 45 years ago and my memory isn't that good. The people living there were Americans who were working at Wethersfield Air Base.

Cheers!

Lee

[.paul.]

i live closer to Maldon. did you ever go there? the whole place is stuck in the 17th century

[Lee.B]

Wife has corrected me. Friends lived in Chelmsford originally then moved to Thaxted into the Priory.
http://www.britishlistedbuildings.co...ory-38-thaxted.