DataGridView Auto-calculate cells In Vb - vb.net

Question

I want to multiply two columns of a datagridview and show the product in Column 3 of the same datagridview.
Example
Column1 - Column2 - Column3
12 2 24
15 2 30
Here is my Code
Private Sub Table1DataGridView1_CellContentClick(sender As Object, e As DataGridViewCellEventArgs) Handles Table1DataGridView1.CellValidated
Try
Dim iCell1 As Integer
Dim icell2 As Integer
Dim icellResult As Integer
iCell1 = Table1DataGridView1.CurrentRow.Cells(1).Value
icell2 = Table1DataGridView1.CurrentRow.Cells(2).Value
If String.IsNullOrEmpty(iCell1) OrElse String.IsNullOrEmpty(icell2) Then Exit Sub
If Not IsNumeric(iCell1) OrElse Not IsNumeric(icell2) Then Exit Sub
icellResult = CDbl(iCell1) * CDbl(icell2)
Table1DataGridView1.CurrentRow.Cells(3).Value = icellResult
Catch ex As Exception
MessageBox.Show(ex.ToString)
End Try
End Sub
It works but a new row is added afterwards. So please help.

Answer 1

An elegant way is to use Databinding (the bread and butter method with datagridviews):
We create a new class, I call MultiplyPair. This class basically has to changable properties, Value1 and Value2.
It also has a third, readonly property called Product.
Whenever Value1 or Value2 changes, we notify any bindingsource that also the product has changed (by implementing INotifyPropertyChanged).
This has several advantages:
You avoid many quirks of the DGV that may arise during manual edits
It's a great way to learn to use databinding (I'm just beginning myself to use the concept thoroughly and it's amazing)
It's easily adaptable: Want also the product, sum and quotient? Just add properties and simple notifications.
You have a clear structure, so other people can understand your code.
You can reuse the whole logic, just bind another datagridview to the same bindinglist and you can display and change the information at multiple locations, with hardly any code.
To use the class we create a Bindinglist(Of MultiplyPair) and bind this list to the datagridview. Then we just ass values to the list and the datagridview is populated automatically. You can even change the values in the Datagridview and the product is automatically updated.
Public Class Form1
Private WithEvents Values As New System.ComponentModel.BindingList(Of MultiplyPair) 'This holds one object for every line in the DGV
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Values = New System.ComponentModel.BindingList(Of MultiplyPair) 'Initialize the list
DataGridView1.AllowUserToAddRows = False 'Disallow new rows, as per your question
DataGridView1.DataSource = Values 'Bind the list to the datagridview
'Add two example lines
Values.Add(New MultiplyPair With {.Value1 = 2, .Value2 = 12})
Values.Add(New MultiplyPair With {.Value1 = 15, .Value2 = 2})
End Sub
End Class
Public Class MultiplyPair
Implements System.ComponentModel.INotifyPropertyChanged
'The first value
Private _Value1 As Double
Public Property Value1
Get
Return _Value1
End Get
Set(value)
_Value1 = value
'Notify not only that Value1 has changed, but also that the Product has changed
Notify("Value1")
Notify("Product")
End Set
End Property
'Same as above
Private _Value2 As Double
Public Property Value2
Get
Return _Value2
End Get
Set(value)
_Value2 = value
Notify("Value2")
Notify("Product")
End Set
End Property
'This will show the product of Value1 and Value2 whenever asked
Public ReadOnly Property Product
Get
Return Value1 * Value2
End Get
End Property
'Helper sub to raise the PropertyChanged event with the given Propertyname
Private Sub Notify(name As String)
RaiseEvent PropertyChanged(Me, New System.ComponentModel.PropertyChangedEventArgs(name))
End Sub
'INotifyPropertyChanged implementation
Public Event PropertyChanged(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
End Class
Edit: To avoid additional rows, set the AllowUsersToAddRows property of the Datagridview to false.