How to sum specific data grid view cell with criteria? - vb.net

Question

I created a DataGridView where I am retrieving data by search customer id. I want to sum values in TextBox when I select some specific CheckBox-es of DataGridView.
But the problem is that it is adding all values in all cells of all rows but it should be like that for example; if Column number is 2, then pending value should be shown once in TextBox not after sum both duplicated received cell, and if Column numbers are different like Column number 1 and Column number 2 and both are selected, sum value should be there in TextBox which is named received from data grid view received cell.
I am attaching image and code also what I am trying to do. can someone guide how to do this?
Private Sub Getvalue()
For Each row As DataGridViewRow In DataGridView1.Rows
If DataGridView1.RowCount > 0 Then
Dim isSelected As Boolean = Convert.ToBoolean(row.Cells(0).Value)
If isSelected Then
Dim pending As String = 0
Dim received As String = 0
Dim final amount As String = 0
For index As Integer = 0 To DataGridView1.RowCount - 1
pending += Convert.ToDouble (DataGridView1.Rows(index).Cells(15).Value)
received += Convert.ToDouble(DataGridView1.Rows(index).Cells(14).Value)
finalamount += Convert.ToDouble(DataGridView1.Rows(index).Cells(12).Value)
Next
Label19.Reset Text()
Label19.Text = pending
Label20.Reset Text()
Label20.Text = received
Label24.Reset Text()
Label24.Text = final amount
If Label19.Text <= 0 Then
Label18.Text = ""
Else
Label18.Text = Val(Label 24.Text - Label 19.Text)
End If
End If
End If
Next
End Sub

Answer 1

First, turn on Option Strict as per my comment.
If there are not rows, your For Each row won't run so there is no need to check the RowCount.
Don't declare your accumulation variables inside the loop. They will be a new variable on each iteration. Your inner loop loops through all rows so, of course, you get the sum of all. Eliminate the inner loop.
I have no idea what Reset Text() is. A method can't have a space in its name. Anyway, it you are adding a new value it isn't necessary to clear the old one. If you do need to clear then set to "". Don't update your labels until after the loop. It is useless to update the user interface on each iteration. It will go by too fast for the user to see and it slows down the code.
In general, you need to do arithmetic or numeric comparisons with numeric types and set .Text properties with String type. The Val method has bee replace with several .net methods. .Parse, .TryParse, Convert. and in vb the CInt, CDec, etc.
Private Sub Getvalue()
Dim pending As Double = 0
Dim received As Double = 0
Dim finalAmount As Double = 0
For Each row As DataGridViewRow In DataGridView1.Rows
Dim isSelected As Boolean = CBool(row.Cells(0).Value)
If isSelected Then
pending += CDbl(row.Cells(15).Value)
received += CDbl(row.Cells(14).Value)
finalAmount += CDbl(row.Cells(12).Value)
End If
Next
Label19.Text = pending.ToString
Label20.Text = received.ToString
Label24.Text = finalAmount.ToString
If pending <= 0 Then
Label18.Text = ""
Else
Label18.Text = (finalAmount - pending).ToString
End If
End Sub
EDIT
Normally you would have a purchase. The purchase would have a table in the database with fields like purchase number, date, customer, etc. You would have another table with purchase details. The details table would have fields like details number (primary key), a foreign key purchase number which must match an entry in the purchase table, an item ID and a price.
When a customer wants to return an item or items from a purchase. You would enter the purchase number and fill your grid from the purchase details table.
Select * From PurchaseDetails Where purchaseNumber = #purchaseNumber
Put the check mark by each item returned and sum up the price column.
Purchase Table
PurchaseID | CustomerID | Date
Purchase Details Table
DetailID | PurchaseID | ItemCode | ItemPrice