Setting .maxlength for a DataGridViewComboBoxColumn

Hi

I have a DataGridView with 2 ComboBoxColumns in it - Description and Action.
I need to be able to limit the amount of characters that users can type into the ComboBoxes within these columns but am not sure how to do it. I have tried:

Code:

---

With Description
            .maxlength = 20
            .Name = "Description"
            .HeaderText = "Description"
            .Width = 275
            .Visible = True
            .ReadOnly = False
            '.AutoComplete = True
            .Items.Add("2nd Homework deadline missed")
End With
        DataGridView1.Columns.Add(Description)
        coladd = True

---

But .maxlength doesn't seem to apply to ComboBoxColumns!

Anyone got any ideas?

Thanks

why not just test add a quick test of length in the keypress event? All you have to do is stop the character being processed if there's 20 already there.

Another way is to do the validation after the text has been entered. For example, we could use the DataGridView1_CellValidating event, do a quick test; If the text entered is less than 21 characters, fine, add it to the list, everything is hunky dory; if not, inform the user and let him / her enter the text again..

As in :

Code:

---

    Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
        Dim NumChars As Integer

        If ColAdd Then
            'Create a New ComboBoxColumn Object, And Cast The dataGridView's Column To That
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(5), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    NumChars = Len(e.FormattedValue)
                    If NumChars < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed ( May HAve To Enter Value Twice )
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)

                    Else
                        MessageBox.Show("Text Too Long")
                    End If
                End If
            End If
        End If
    End Sub

---

I hope this info was useful.

Of course, if you're using the extended DGV which HanneS and I put together, you could add it into the validation:

Code:

---

      Private Sub DGV_Validate(ByVal sender As Object, ByVal e As DataGridViewCellValidatingEventArgs) Handles MyBase.CellValidating
            If TypeOf (Me.Columns(e.ColumnIndex)) Is DataGridViewComboBoxColumn Then
                Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(Me.Columns(e.ColumnIndex), DataGridViewComboBoxColumn)
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    If Len(e.FormattedValue) > 20 Then
                        Throw New ArgumentException("The Value is too long")
                    Else
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        Me.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)
                    End If
                End If
            End If
        End Sub

---

Cheers guys - glad you remembered my code!

Will try out your suggestions and let you know how I get on!

Hi Guys - no joy I'm afraid

The code I am using is below:

Code:

---

Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
        Dim Numchars As Integer 'new
        If coladd Then

            'Create a New ComboBoxColumn Object, And Cast The dataGridView's Column To That
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(9), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    Numchars = Len(e.FormattedValue)
                    If Numchars < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed ( May HAve To Enter Value Twice )
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)

                    Else
                        MessageBox.Show("Description Text Too Long")
                    End If
                End If
            End If

        Else
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(10), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    Numchars = Len(e.FormattedValue)
                    If Numchars < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed ( May HAve To Enter Value Twice )
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)

                    Else
                        MessageBox.Show("Action Text Too Long")
                    End If
                End If
            End If
        End If
    End Sub

---

Thanks for the help so far . . . . .

What error are you getting, and when? This code segment compiles fine on my machine, but it may not work in context.

Plus, if I remember correctly, if is colAdd is true then the input is not generated by the user, so you don't need to check it? Or am I thinking of a colAdd from a different project?

also, a slightly neaten version of the code you posted (Mainly perfectionist things).
The only important change is the inclusion of e.Cancel = True after the messageboxs.

Code:

---

    Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
        If coladd Then

            'Create a New ComboBoxColumn Object, And Cast The dataGridView's Column To That
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(9), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    If Len(e.FormattedValue) < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed (May Have To Enter Value Twice)
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)
                    Else
                        MessageBox.Show("Description Text Too Long")
                        e.Cancel = True
                    End If
                End If
            End If

        Else

            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(10), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    If Len(e.FormattedValue) < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        'Make Sure Value Stays Displayed (May Have To Enter Value Twice)
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)
                    Else
                        MessageBox.Show("Action Text Too Long")
                        e.Cancel = True
                    End If
                End If
            End If
        End If
    End Sub

---

I think you are thinking of a CollAdd from a different project!

The code does not produce an error - it just adds the entry to the ComboBox anyway! It just seems to work as normal as if I hadn't added the new code.

Look at e.Cancel (see my previous post (post 8))

EDIT: clearly I'm not thinking, because even if that isn't there, the item should never be added. It must be something else. Have you tried stepping through it and checking the value and length of e.FormattedValue?

Yep - that's true. Will step though now and see what is happening ;)

Doh - I am being thick. I haven't stepped through any code for a loooonnnnnggg time and now I can't remember how to isolate the piece of code (e.FormattedValue) that I need the value of!!

Can you give me some pointers??

Cheers

I personally use the Watch windows (Menu Bar -> Debug -> Windows -> Watches) as then, when debugging, you can specify expressions to watch. Other methods such as just selecting an expression and mousing over, or the Local or Auto windows (same menu) also do the job.

Have tried but setting a breakpoint on the following line but nothing happens so I guess it somehow isn't executing that line?

Code:

---

comboBoxColumn.Items.Add(e.FormattedValue)

---

The code just executes as normal and doesn't stop at the line. The item does get added to the ComboBox though and when I subsequently save, it gets saved to the Spreadsheet too!

Also, when I goto Debug --> Windows, all I get is Immediate, Breakpoints and Outputs. I don't have Watch

Anyone?????

Hi again! :)

Can you perhaps show the complete code segment ¿
Is it still the same app I'm thinking about ¿
There may be an outside influence causing this, but the code I supplied worked as you needed it, javajawa's as well.
This is indeed an odd one.. :)

Hi Hannes thanks for the reply

It is indeed the same app you are thinking about. The full code segment for the Cell Validating section is:

Code:

---

Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
        Dim Numchars As Integer 'new
        If coladd Then

            'Create a New ComboBoxColumn Object, And Cast The dataGridView's Column To That
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(9), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    Numchars = Len(e.FormattedValue)
                    If Numchars < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed ( May HAve To Enter Value Twice )
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)

                    Else
                        MessageBox.Show("Description Text Too Long")
                        e.Cancel = True
                    End If
                End If
            End If

        Else
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(10), DataGridViewComboBoxColumn)
            'If In ComboBoxColumn
            If (e.ColumnIndex = comboBoxColumn.DisplayIndex) Then
                If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                    Numchars = Len(e.FormattedValue)
                    If Numchars < 21 Then
                        'Add The Text Entered By The User
                        comboBoxColumn.Items.Add(e.FormattedValue)
                        '  Make Sure Value Stays Displayed ( May HAve To Enter Value Twice )
                        DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)

                    Else
                        MessageBox.Show("Action Text Too Long")
                        e.Cancel = True
                    End If
                End If
            End If
        End If
    End Sub

---

Thanks for taking a look Hannes

OK, Change your CellValidating event to look like this code, precisely :

Code:

---

    Private Sub DataGridView1_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles DataGridView1.CellValidating
        Dim NumChars As Integer

        If TypeOf (DataGridView1.Columns(e.ColumnIndex)) Is DataGridViewComboBoxColumn Then
            Dim comboBoxColumn As DataGridViewComboBoxColumn = CType(DataGridView1.Columns(e.ColumnIndex), DataGridViewComboBoxColumn)
            If (Not comboBoxColumn.Items.Contains(e.FormattedValue)) Then
                NumChars = Len(e.FormattedValue)
                If NumChars > 20 Then
                    MessageBox.Show("The Value is too long")
                Else
                    comboBoxColumn.Items.Add(e.FormattedValue)
                    DataGridView1.Rows(e.RowIndex).Cells(e.ColumnIndex).Value = comboBoxColumn.Items(comboBoxColumn.Items.Count - 1)
                End If
            End If
        End If

    End Sub

---

It is mainly javajawa's code, but both options supplied would've worked.
Make sure it reflects this precisely, run it, test it, see if it works, and let us know :)

I'd still personally save declaring the variable, especially if it's only used once!
Also, the code that I've been posting has been working on the assumption that you want the conditions for all DGVComboCols. Hannes' code is of course specific to the two columns.

Just a thought - you're not using both the DGVNew class and that code - because that's the only thing I can think of that would allow the value to be added without the breakpoint being fired, as it would be added by the DGVNew code and then not added again as the combobox would then contain the item...

I really hope I'm making some sense here (It still feels a bit on the early side, even though I don't have enough time to get to my first lecture...

HI Hannes

That works great - not a clue why it didn't work yesterday. Even me with my limited skills could see that it should have worked!!

Now I just have to stop the value entered from disappearing when the message pops up so that they don't have to type it in again!

Thanks as always for your help guys ;)

For stopping it disappearing, I'd look into setting the e.Cancel property. I think tha if you set it to true, the underlying validation event won't be called.