title: Object cannot be cast from DBNull to other types
body: <p>i was trying to get the sum of the row items in a datagridview<br>
  this is my code  </p>
  
  <pre><code> Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
  
  
      If DataGridView1.RowCount &gt; 1 Then
          Dim RegFee As Integer = 0
          Dim MisFee As Integer = 0
          Dim TuiFee As Integer = 0
          Dim PtcaFee As Integer = 0
          Dim CompFee As Integer = 0
  
          For index As Integer = 0 To DataGridView1.RowCount - 1
              RegFee += Convert.ToInt32(DataGridView1.Rows(index).Cells(4).Value)
              MisFee += Convert.ToInt32(DataGridView1.Rows(index).Cells(5).Value)
              TuiFee += Convert.ToInt32(DataGridView1.Rows(index).Cells(6).Value)
              PtcaFee += Convert.ToInt32(DataGridView1.Rows(index).Cells(7).Value)
              CompFee += Convert.ToInt32(DataGridView1.Rows(index).Cells(8).Value)
  
          Next
          DataGridView2.Rows.Add("Registration Fee", RegFee)
          DataGridView2.Rows.Add("Miscellaneous Fee", MisFee)
          DataGridView2.Rows.Add("Tuition Fee", TuiFee)
          DataGridView2.Rows.Add("PTCA Fee", PtcaFee)
          DataGridView2.Rows.Add("Computer Fee", CompFee)
  
      End If
  End Sub  
  </code></pre>
  
  <p>but i'm having an error:<br>
  Object cannot be cast from DBNull to other types.<br>
  can you help me??? </p>