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 <>