Question : How do I test for a null value in a datagridview cell

I know how to populate a text box form a datagridviewcell, but I am having trouble testing for null values in a datagridview cell. I've tried several versions of the following but to no avail
If row.Cells(4).Value NOT DBNull.Value Then
cboTechnologySetType.Text = row.Cells(4).Value.ToString
End If

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If dgvTechnologySets.Rows.Count > 0 Then
                Dim rowindex As Integer = dgvTechnologySets.CurrentCell.RowIndex
                Dim row As DataGridViewRow = dgvTechnologySets.Rows(rowindex)
                Dim cell As DataGridViewCell = row.Cells(2)
                Dim strTechCode As String = (cell.Value).ToString
                txtTechnologySetCode.Text = strTechCode
                'if row.Cells(3).Value.ToString != vbNull then
                '    txtTechnologySetName.Text = row.Cells(3).Value.ToString
                'End If
                'If row.Cells(4).Value.ToString = DBNull.Value Then
                '    cboTechnologySetType.Text = row.Cells(4).Value.ToString
                'End If
                If row.Cells(5).Value = True Then
                    chkIsActive.CheckState = CheckState.Checked
                Else
                    chkIsActive.CheckState = CheckState.Unchecked
                End If

            End If

Answer : How do I test for a null value in a datagridview cell

A datagridview textbox cell doesn't have a null value, it have an empty string value: ""

So, if I got you right:

If dgvTechnologySets.Rows.Count > 0 Then
Dim rowindex As Integer = dgvTechnologySets.CurrentCell.RowIndex
Dim row As DataGridViewRow = dgvTechnologySets.Rows(rowindex)
Dim cell As DataGridViewCell = row.Cells(2)
Dim strTechCode As String = (cell.Value).ToString
txtTechnologySetCode.Text = strTechCode
If row.Cells(3).Value <> "" Then
txtTechnologySetName.Text = row.Cells(3).Value.ToString
End If
If row.Cells(4).Value = "" Then
cboTechnologySetType.Text = row.Cells(4).Value.ToString
End If
If row.Cells(5).Value = True Then
chkIsActive.CheckState = CheckState.Checked
Else
chkIsActive.CheckState = CheckState.Unchecked
End If

End If

By the way the not-equal in vb isn't != but <>