Hello Friends!
I need your help, I have a strnge error.....
 
private void cbDesMensalidade_SelectedValueChanged(object sender, EventArgs e)
        {
            if (cbDesMensalidade.SelectedIndex != -1)
            {
                this.tbValorDesc.Text = (nc.getValorAluno(tbRefCadastro.Text) - (nc.getValorAluno(this.tbRefCadastro.Text) * ((Convert.ToInt32(cbDesMensalidade.SelectedValue)) / 100))).ToString();
            }
        } 
 
The error is "Unable to cast object of type 'RH_2013.DAL.CombAdd' to type 'System.IConvertible'." 
 
Please Help