重复性输入检测

DataRow[] foundRowDept = this.dtbDept.Select("dept_name ='" + cboDept.Text + "'");
                                DataRow[] foundRowSubsidiary = this.dtbSubsidiary.Select("subsidiary_name ='" + cboSubsidiary.Text + "'");
                                DataRow[] foundRowRoleInfm = this.dtbRoleInfm.Select("subsidiary_name ='" + cboSubsidiary.Text + "'and dept_name ='" + cboDept.Text + "' and role_name='" + txtRoleName.Text.Trim() + "'");
                                if (foundRowRoleInfm.Length > 0)
                                {
                                    MessageBox.Show(cboSubsidiary.Text + cboDept.Text + "下已有角色：" + txtRoleName.Text.Trim() + "!!");
                                    return;
                                }