Question

I am trying to sum the values from Datagridview1(Table1) and save it to Datagridview2(Table2)

both DGVs are Databound and both have the same 2 columns Name, Quantity.

On Childform1(DGV1) I have a Textbox1 and a Post button.

The user must input a Name on Textbox1 and click Post, then all the Quantity on DGV1 must be summed up that has the same Name as entered on Textbox1.

ex:

Table1

Name | Quantity
 a       10
 b        5
 a       10
 b        5

After pressing POST button

Table 2

Name | Quantity
 a        20
 b        10

Codes

    Dim occurences As New Dictionary(Of String, Double)
    Dim oTempObjects As New List(Of DataGridViewRow)

    MasterForm.oTransferRows = oTempObjects

    For Each xRow As DataGridViewRow In Datagridview1.Rows

        If (Not xRow.Cells("GVName").Value Is Nothing AndAlso xRow.Cells("GVName").Value.ToString() = TextBox1.Text) Then

            oTempObjects.Add(xRow)
        End If
    Next

    Dim _Name As New List(Of String)

    For Each xRows In MasterForm.oTransferRows

        _Name.Add("'" & xRows.Cells("GVName").Value.ToString() & "'")


        Dim inClause1 As String = String.Join(",", _Name.ToArray())
        Dim _sqlUpdate As String = String.Format("UPDATE tested SET Posted = @Posted WHERE Name IN ({0})", inClause1)

        Using _conn As New MySqlConnection("Server = localhost; Username= root; Password =; Database = test")
            Using _commm As New MySqlCommand()
                With _commm

                    .CommandText = _sqlUpdate
                    .Connection = _conn
                    .CommandType = CommandType.Text
                    .Parameters.AddWithValue("@Posted", "Yes")

                End With
                Try

                    _conn.Open()
                    _commm.ExecuteNonQuery()

                Catch ex As MySqlException

                    MsgBox(ex.StackTrace.ToString)

                End Try

                _conn.Close()

            End Using
        End Using

        If (occurences.ContainsKey(xRows.Cells(1).Value.ToString())) Then

            occurences(xRows.Cells(1).Value.ToString()) = Double.Parse(occurences(xRows.Cells(1).Value.ToString()).ToString()) + Double.Parse(xRows.Cells(4).Value.ToString())

        Else

            occurences.Add(xRows.Cells(1).Value.ToString(), Double.Parse(xRows.Cells(4).Value.ToString()))
        End If

    Next

    For Each KVP As KeyValuePair(Of String, Double) In occurences
        oChildForm2.DataGridView2.Rows.Add(New Object() {KVP.Key, KVP.Value})
    Next

    Dim xlist As List(Of KeyValuePair(Of String, Double)) = occurences.ToList

    For Each pair As KeyValuePair(Of String, Double) In occurences


        Dim oUpdateString = String.Format("Insert Into testing (Name, Quantity) VALUES (@iName, @iQty)")
        Using _conn As New MySqlConnection("Server = localhost; Username= root; Password =; Database = test")
            Using _commm As New MySqlCommand()
                With _commm

                    .CommandText = oUpdateString
                    .Connection = _conn
                    .CommandType = CommandType.Text
                    .Parameters.AddWithValue("@iName", pair.Key)
                    .Parameters.AddWithValue("@iQty", pair.Value)
                End With
                Try

                    _conn.Open()
                    _commm.ExecuteNonQuery()

                Catch ex As MySqlException

                    MsgBox(ex.StackTrace.ToString)

                End Try

                _conn.Close()

            End Using
        End Using
    Next

This code only sums the same Name on the DGV1 on the first click and saves it on DGV2.

but for example I add another data on DGV1 with the same name,

I want the QUANTITY of the newly added data to add to the current sum of the existing data on DGV2.

A little help with this too would be really awesome.**

Ex:

TABLE 2

Name | Quantity
 a       20
 b       10

Then I add data on Table 1

Table1

Name | Quantity
  a       20
  b       10

After Pressing Post

Table2

Name | Quantity
 a        40
 b        20

Answer 1

Check the Posted column when iterating through your rows to see if a row has been posted or not:

For Each xRows In MasterForm.oTransferRows.Where(Function(x) x.Cells("Posted").Value.ToString() = "No")

Then use the following psuedo-logic to write your code:

 'code to select data - select name from testing where name = 'Product1'
 'if(dr.Read())
 'update goes here
 'Else
 ' insert goes here
 'End if