Check for Duplicate in DataGridView

[Alexandrumbm]

Hello to you all...

I have a DataGridView1 that takes values from an MDB.
I have a TextBox and a "Save" CommandButton to add new data to the database.

How do i prevent duplicates entry to the DatagridView ?!

Please help me!!!!!!

 

[chrissie1]

Usually you first of all put a constraint on the databse.

And then if you want to be nice to your users you do a select for the value in the textbox and if you get more then 0 result you know it is already in there and then you show a little messagebox to say that they shouldn't do that. If they do it correct you reward them.

Christiaan Baes
Belgium

"My old site" - Me

 

[SHelton]

One of two ways I can think of:

1. Use the CellValidating event for the key column and check if the value already exists. This prevents the user trying to enter a duplicate.

2. Use DataView.ToTable when the user clicks the save button. This has a overload that returns a datatable containing distinct values of a specified column. If the distinct datatable has less rows than the datagridview, there are duplicates.

 

[Alexandrumbm]

Do you have any sample about it ?! Please... i am not newb very newb to VB. I have search on many forums and i have googleit many many hours!

Please!!!

 

[SHelton]

Very quick examples, please excuse any slack coding! Both assume that the distinct column in the source datatable is called DistinctCol and is of an integer type.

Example 1 (CellValidating event)

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

        If DataGridView1.Columns(e.ColumnIndex).DataPropertyName = "DistinctCol" AndAlso e.FormattedValue.ToString() <> DataGridView1(e.ColumnIndex, e.RowIndex).Value.ToString() Then

            Dim dt As DataTable = CType(DataGridView1.DataSource, DataTable)

            Dim rows As DataRow() = dt.Select("DistinctCol = " & e.FormattedValue)

            If rows.Length > 0 Then

                MessageBox.Show("This value is already used.")

                e.Cancel = True

            End If

        End If

    End Sub

Example 2: (DataView.ToTable)

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim dt As DataTable = CType(DataGridView1.DataSource, DataTable)

        Dim dv As New DataView(dt)

        Dim distinct As DataTable = dv.ToTable(True, New String() {"DistinctCol"})

        If distinct.Rows.Count <> dt.Rows.Count Then

            MessageBox.Show("There are duplicate values.")

        End If

    End Sub