using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Service
{
    public static class DbExtensions
    {
        // 安全读取 string
        public static string SafeGetString(this IDataRecord reader, string fieldName)
            => reader[fieldName] as string; // DBNull.Value as string → null

        // 安全读取可空值类型（如 int?）
        public static T? SafeGetValue<T>(this IDataRecord reader, string fieldName)
            where T : struct
        {
            var val = reader[fieldName];
            return (val == DBNull.Value) ? null : (T?)val;
        }
        public static void AddParameter(this IDbCommand cmd, string name, object value)
        {
            var param = cmd.CreateParameter();
            param.ParameterName = name;
            param.Value = value ?? DBNull.Value; // 自动转换
            cmd.Parameters.Add(param);
        }
    }
}