Error removing data in Gridview asp.net c #

This is my method of deleting from gridview:

 protected void TabelaAlimentos_DeleteRow(object sender, GridViewCommandEventArgs e)
{
    if(e.CommandName == "Delete")
    {
        GerenciarAlimentacaoController controller = new GerenciarAlimentacaoController();

        int index = Int32.Parse((string)e.CommandArgument);
        int id = Int32.Parse(TabelaAlimentos.Rows[index].Cells[0].Text);

        Alimento alimento = (Alimento)controller.pesquisar(id, "Alimentos");
        controller.deletar(alimento);
        TabelaAlimentos.DeleteRow(index);
        TabelaAlimentos.DataBind();



        FileInfo file = new FileInfo(Server.MapPath("~/img/Alimentos/") + alimento.imagemAlimento);

        file.Delete();

        Response.Write("<script language='javascript'> alert('Alimento Removido com Sucesso!'); window.location=('gerenciaralimentacao.aspx'); </script>");


    }
}

The code normally runs without error, but when it exits the method the error is generated.