Add quantity if the DataGridView item already exists - vb.net

Question

I have created a cart using a DataGridView and on the add to cart button I have this code:
Dim a As Integer
Dim total As Integer
Dim b As Integer
a = TextBox2.Text
b = NumericUpDown56.Value
total = a * b
ShoppingCart.DataGridView1.Rows.Add(Me.Label11.Text, Me.TextBox2.Text, Me.NumericUpDown56.Value, total)
Me.Hide()
ShoppingCart.Show()
How can I add quantity if I re-added the same item?

Answer 1

It is a little hard to answer this without knowing quite what the textbox and updowncounter do... but assuming you only expect the updown counter to change...
You can iterate through the data and hunt for the same text in the first column
Dim a As Integer
Dim total As Integer
Dim b As Integer
a = TextBox2.Text
b = NumericUpDown56.Value
total = a * b
Dim Updated As Boolean
For Each row As DataGridViewRow In ShoppingCart.DataGridView1.Rows
If CType(row.Cells(0).Value, String) = Me.Label11.text Then
row.Cells(2).Value = CType(row.Cells(0).Value, Integer) + b
row.Cells(3).Value = CType(row.Cells(3).Value, Integer) + total
Updated = True
Exit For
End If
Next
If Not Updated Then ShoppingCart.DataGridView1.Rows.Add(Me.Label11.Text, Me.TextBox2.Text, Me.NumericUpDown56.Value, total)
Me.Hide()
ShoppingCart.Show()
Though personally I'd bind the datagridview to a of List(of T) (t = a class that retains your properties) and search / modify that instead, then rebind the list.
Something along these lines...
Private Class cls_Cart_Item
Public Property Item_Name As String
Public Property Whatever_TExtbox2_IS_SUpposed_to_be As Integer
Public Quantity As Integer
Public Sub New(wName As String, wWhatever_TExtbox2_IS_SUpposed_to_be As Integer, wQuantity As Integer)
Item_Name = wName
Whatever_TExtbox2_IS_SUpposed_to_be = wWhatever_TExtbox2_IS_SUpposed_to_be
Quantity = wQuantity
End Sub
Public ReadOnly Property Total As Integer
Get
Return Whatever_TExtbox2_IS_SUpposed_to_be * Quantity
End Get
End Property
End Class
Private Cart As New List(Of cls_Cart_Item)
Private Sub Add_Or_Update()
ShoppingCart.datagridview1.datasource = Nothing
Dim a As Integer
Dim total As Integer
Dim b As Integer
a = TextBox2.Text
b = NumericUpDown56.Value
Dim Item As New cls_Cart_Item = Cart.Find(Function(x) x.Item_Name = Me.Label11.Text)
If Item Is Nothing Then
Cart.Add(New cls_Cart_Item(Me.Label11.Text, a, b))
Else
Item.Quantity += b
End If
Me.Hide()
ShoppingCart.datagridview1.datasource = Cart
End Sub
Though it's hard to tell from your question where this code is coming from relative to the daraviewgrid.