checkbox from datagridview to textbox - vb.net

Question

A new issue !!
I have a checkbox column in the datagridview and also a column named "partqty" which displays the quantity of materails available.. I would want that when the user checks on the checkbox, the quantities of checked rows should be added and displayed in the textbox..
I tired something like this.. But it displays 0(zero) in the textbox.. Please help..
Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click
'For Each _rw As DataGridViewRow In dataGridView1.Rows
' If _rw.Cells(0).Value = True Then
Dim totalSum As Integer
For i As Integer = 0 To HemDatabase1DataSet5.Tables(0).Rows.Count - 1
totalSum += HemDatabase1DataSet5.Tables(0).Rows(i).Item("partqty")
Next
textBox5.Text = totalSum.ToString()
' End If
'Next
End Sub
Hey !! This is something i could think upon trying !! however, there is no error during compile time, but there is an error at runtime, which says :
Operator '+' is not defined for type 'DBNull' and type 'Boolean'
Here is the code i tried :
For Each _rw As DataGridViewRow In dataGridView1.Rows
If _rw.Cells(0).Value = True Then
Dim totalSum As Integer
For i As Integer = 0 To dataGridView1.Rows.Count - 1
totalSum += dataGridView1.Rows(i).Cells(5).Value
Next
textBox5.Text = totalSum.ToString()
End If
Next
It gives error on this line :
totalSum += dataGridView1.Rows(i).Cells(5).Value

Answer 1

You first problem is that you are trying to add apples and oranges together.
In the line:
totalSum += dataGridView1.Rows(i).Cells(5).Value
totalSum is an integer while the Value property of a DataGridView cell is of type object.
This is a similar problem to what you see when trying to use the DataTable except there your Item property is givin you a DBNull rather than an object back.
Here is the code that you want (I'm mainly a C# dev so the VB.Net might be lacking elegance but it works).
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim sum As Integer
sum = 0
For Each row As DataGridViewRow In DataGridView1.Rows
Dim current As Integer
If Integer.TryParse(row.Cells("OrderQty").Value.ToString, current) Then
sum += current
End If
Next
TextBox1.Text = sum.ToString
End Sub
Some things worth noting about that code:
I use a For Each rather than a for. The two perform basically identically but I find the foreach more readable
I use Integer.TryParse on the cell value before using it. This is safer than just casting the cell value directly.
Rather then using column indexes which is a little fragile I use column names.
With your check on whether or not the checkbox is checked you can do something similar:
Boolean.TryParse(row.Cells("IsChecked").Value.ToString, cb)
One final point to note is that if you try to execute this code in the cellclick method of the DataGridView you will run into problems - the checkbox state is not committed until after the cellclick, so the most recently checked cell will not get added to your count. Instead you will want to handle the CellDirtyStateChanged and commit the edits, then doing the sum in the CellValueChanged handler.
To illustrate that try this code:
Private Sub dgv_CellContentClick(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs) Handles DataGridView1.CellClick
Dim sum As Integer
sum = 0
Dim cb As Boolean
cb = False
If DataGridView1.Columns(e.ColumnIndex).Name <> "IsChecked" Then
Return
End If
For Each row As DataGridViewRow In DataGridView1.Rows
If Boolean.TryParse(row.Cells("IsChecked").Value.ToString, cb) Then
If cb Then
Dim current As Integer
If Integer.TryParse(row.Cells("OrderQty").Value.ToString, current) Then
sum += current
End If
End If
End If
Next
TextBox1.Text = sum.ToString
End Sub
The sum will always lag one click behind (actually in VB.Net it appears to just nor really work - but I'm more a c# dev so that could be me missing something).
Instead you want:
Sub dataGridView1_CurrentCellDirtyStateChanged( _
ByVal sender As Object, ByVal e As EventArgs) _
Handles DataGridView1.CurrentCellDirtyStateChanged
If DataGridView1.IsCurrentCellDirty Then
DataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit)
End If
End Sub
' If a check box cell is clicked, this event handler disables
' or enables the button in the same row as the clicked cell.
Public Sub dataGridView1_CellValueChanged(ByVal sender As Object, _
ByVal e As DataGridViewCellEventArgs) _
Handles DataGridView1.CellValueChanged
If DataGridView1.Columns(e.ColumnIndex).Name = "IsChecked" Then
Dim sum As Integer
sum = 0
Dim cb As Boolean
For Each row As DataGridViewRow In DataGridView1.Rows
If Boolean.TryParse(row.Cells("IsChecked").Value.ToString, cb) Then
If cb Then
Dim current As Integer
If Integer.TryParse(row.Cells("OrderQty").Value.ToString, current) Then
sum += current
End If
End If
End If
Next
TextBox1.Text = sum.ToString
End If
End Sub

Answer 2

This is the code that worked..
Dim iSselected As Boolean
Dim CurrentCellValue As String
Dim CumulativeSummer As Integer
Dim i As Integer
With Me.dataGridView1
For i = 0 To .RowCount - 1
iSselected = .Rows(i).Cells(0).Value
CurrentCellValue = .Rows(i).Cells(5).Value
If CurrentCellValue = "" Then CurrentCellValue = 0
If iSselected = True Then
CumulativeSummer += Convert.ToInt32(CurrentCellValue)
End If
Next
End With
Me.textBox5.Text = CumulativeSummer
Thank u for your help !! :)