/// <summary>
/// 单个值返回值
/// </summary>
/// <param name="sql"></param>
/// <param name="param"></param>
/// <param name="transaction"></param>
/// <param name="commandTimeout"></param>
/// <param name="commandType"></param>
/// <returns></returns>
public async Task <T> ExecuteScalarAsync(string sql, object param = null, IDbTransaction transaction = null, int?commandTimeout = default(int?), CommandType?commandType = default(CommandType?))
{
return(await modelDal.ExecuteScalarAsync(sql, param, transaction, commandTimeout, commandType));
}