Question

How to prevent entering duplicate record in DataGridView?

Asked by: adlink_la

Hello all,
I am using a DataGridView in unbound mode.  I have some code in the RowValidating event that works well to ensure that required values are present and not too long, etc.  This prevents the user from leaving the row until the data entered is valid or the Esc key is pressed.  Next, I have code in the RowValidated event to call the Update procedure for existing rows and the Insert procedure when a user enters a new row.

What I need to do is prevent the user from entering a record that already exists.  I tried having my insert procedure do the check and then pass back a message indicating that the record already exists.  This is working.  However, the problem is that duplicate record that the user just entered remains in the grid.  I tried putting the following in right after doing the insert:

grd.Rows.RemoveAt(e.RowIndex)

However, I get an error saying that this operation is not allowed in the RowValidated event.  I don't really want to put code in the RowValidating event to check for duplicates because that event fires on every keypress and I don't want that many calls to the database.

As I said, my Insert procedure already handles checking for an existing record and will not insert a duplicate.  All I need is to be able to remove the row that the user entered into the grid if it happens to be a duplicate and was not inserted.  Basically, I want the user to see the row disappear after the message is displayed indicating that the record was a duplicate, so that it is obvious and also because if it is not removed then the grid will contain two identical rows.

I've also tried the RowsAdded and the UserAddedRow events.  But these fire on the first keypress in the 'New Row' row.  I need to do the check after all of the data has been entered on the row.

So what event can I use to do this?  Sorry for the long post.

Thanks in advance.

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Asked On
2008-09-22 at 19:26:02ID23753678
Tags

Microsoft

,

Visual Studio 2005

,

SP1

,

DataGridView

,

VB.NET

Topic

Microsoft Visual Basic.Net

Participating Experts
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Comments
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Answers

 

by: MuhammadKashifPosted on 2008-09-22 at 22:08:03ID: 22546574

Hi adlink_la,

RowValidating is not fired at every keypress. It is fired when a row is committed.

Following events displays error when you try to delete row in these events.
CellEnter
CellLeave
CellValidating
CellValidated
RowEnter
RowLeave
RowValidating
RowValidated

So you should use CellValueChanged event and also you can have you validation in this event.

 

by: adlink_laPosted on 2008-09-23 at 11:23:24ID: 22552391

Thanks for the reply, Muhammad.  Yes, you are correct.  The RowValidating event is only firing once, not for every keypress as I thought.  I looked into using the CellValueChanged event but it is not possible to cancel in that event.  

I created a function to check whether a record exists and tried adding that check to the RowValidating event as this is where I need to do the check in order to have the ability to cancel if needed.  However, the check returns true for all existing records in the grid.  I need a way to distinguish between existing records and a new row that the user is adding so that I can do this check for that row only.

Thanks.

    Private Sub grd_RowValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellCancelEventArgs) Handles grd.RowValidating
        Dim row As DataGridViewRow = grd.Rows(e.RowIndex)
        Dim FNameCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.FirstName).Index)
        Dim LNameCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.LastName).Index)
 
        row.ErrorText = ""
        FNameCell.ErrorText = ""
        LNameCell.ErrorText = ""
 
        'Do not try to validate if the cursor is in the "New Row" row.  This row contains 
        '  no data yet.  If we try to validate, the cursor will get locked in that row until 
        '  the user enters some valid values.  This little bit of code will let the user 
        '  arrow back up off of that row without having to enter any data.
        If grd.Rows(e.RowIndex).IsNewRow() Then
            Return
        End If 'grd.Rows(e.RowIndex).IsNewRow()
 
 
        '**********************************************************************************
        '**********************************************************************************
        '**********************************************************************************
        'After the first key is pressed in the "New Row" row, a row is added to the grid and
        '  editing occurs there.  The cursor will then be one row above the "New Row" row.  
        '  Hence, the above check will return false as soon as the user begins entering data 
        '  for a new record.
        '
        'The check for duplicate records must be done here as it is not possible to cancel 
        '  in the other events.  However, the following code will also flag an existing 
        '  record as a duplicate just by attempting to arrow through the rows.  This locks 
        '  the cursor in the row indefinitely.
        '
        'What I need is a way to distinguish existing rows from a row that the user is
        '  adding.
        '**********************************************************************************
        '**********************************************************************************
        '**********************************************************************************
 
        'See if this record already exists.  If so, don't let the user leave the row without 
        '  either changing it or hitting ESC.
        'If frmMain.m_bll.opTechs_isExists(FNameCell.Value, LNameCell.Value) Then
        '    row.ErrorText = "Record already exists"
        '    e.Cancel = True
        'End If
 
        FNameCell = Nothing
        LNameCell = Nothing
        row = Nothing
    End Sub
                                              
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by: MuhammadKashifPosted on 2008-09-23 at 21:15:41ID: 22556703

you can have any hidden column and setting the value to true if user enters new row.

OR

you can change the background color of the newly added rows and then you can check if it is this color then chekc.....

 

by: adlink_laPosted on 2008-09-24 at 08:56:23ID: 22561040

The point is that I don't want to let the row be added and then have to go back and delete it.  I want to use the functionality that is built into the grid, which is to cancel the row before it is added.  Isn't there some way to tell if the row that is validating is a new row?

I need a clean solution because I have a few forms that have similar functionality for different tables and I need to prevent the user from entering duplicates in all of them.

Thanks again.

 

by: adlink_laPosted on 2008-09-24 at 15:19:36ID: 22564604

Okay, I do actually have a hidden column already that I can check.  The ID column will have a value for all existing rows.  When a user adds a row, the insert procedure returns the ID value of the newly created record which is then written to the ID column in the grid.  So in the RowValidating event, if the ID value is Nothing then I can check to see if the record already exists in the database and cancel if needed.  Woohoooo!!  That'll work!

Thanks for the help.

Dim idCell As DataGridViewCell = row.Cells(grd.Columns(ColumnEnum.TechID).Index)
If idCell.Value Is Nothing Then
    'This is a new row that is just being added by the user.
 
    'See if this record already exists.  If so, don't let the user leave the row 
    '  without either changing it or deleting it.
    If frmMain.m_bll.opTechs_isExists(FNameCell.Value, LNameCell.Value) Then
        row.ErrorText = "Record already exists"
        'Setting Cancel to True here will stop the RowValidated event from firing,
        '  so the record will not be inserted into the database.
        e.Cancel = True
        Return
    End If
 
End If
                                              
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by: adlink_laPosted on 2008-09-24 at 15:22:05ID: 31499119

Thanks again for pointing me in the right direction.

20120131-EE-VQP-002

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