Throws exception when for row update from datagridview by textboxes

See more:

C#

DataGridView

exceptions

After update button is clicked, I would want to update the selected row in datagridview and sql database. This is my code but however it throws me an exception, "Index was out of range. Must be non-negative and less than the size of the collection."
Please advise me, thank you :)

private void UpdateButton_Click(object sender, EventArgs e)
{
  if (tbx_Name.Text.Equals("") || tbx_Desc.Text.Equals(""))
  {
      MessageBox.Show("Fill in all forms");

  }
  else
  {
      int selectedRow;
      selectedRow = dataGridView1.SelectedRows[0].Index;
      Bag newBag= new Bag();
      newBag.Name = tbx_Name.Text;
      newBag.Desc = tbx_Desc.Text;
      dataGridView1.Rows[selectedRow].SetValues(tbx_Name.Text, tbx_Desc.Text);

      if (DBManager.UpdateBag(newBag) == 1)
      {
          MessageBox.Show("Update is successful");
      }
       else
         {
           MessageBox.Show("Update is not successful");
           }
  }

[edit]Code block added[/edit]