Problems changing color of rows in a DataGrid in C # Wpf

I am having problems changing the color of the DataGrid rows, I use the following function

int i = 0;
private void gvDados_LoadingRow(object sender, DataGridRowEventArgs e)
{
   DataGridRow rowContext = e.Row;
   if (rowContext != null)
   {
      string Situacao = dt.Rows[i]["Situacao"].ToString();
      if (Situacao.Equals("V"))
      {
         SolidColorBrush brush = new SolidColorBrush(Color.FromArgb(100, 255, 104,0));
         rowContext.Background = brush;
      }
      else
      {
         SolidColorBrush brush = new SolidColorBrush(Color.FromArgb(100, 255, 232,0));
         rowContext.Background = brush;
      }

      i++;
   }
}

So far so good, I can adjust the colors according to what I want, the problem in question is when I use the Horizontal Scroll Bar to go down the registers or climb, then all the colors are misconfigured appearing at random. How can I solve this problem so things do not change when scrolling?