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

namespace Bxlz.Common
{
    /// <summary>    
    /// 实体转换辅助类    
    /// </summary>    
    public class ModelConvertHelper<T> where T : new()
    {
        public static IList<T> ConvertToModel(DataTable dt)
        {
            // 定义集合    
            IList<T> ts = new List<T>();

            // 获得此模型的类型   
            Type type = typeof(T);
            string tempName = "";

            foreach (DataRow dr in dt.Rows)
            {
                T t = new T();
                // 获得此模型的公共属性      
                PropertyInfo[] propertys = t.GetType().GetProperties();
                foreach (PropertyInfo pi in propertys)
                {
                    tempName = pi.Name;  // 检查DataTable是否包含此列    

                    if (dt.Columns.Contains(tempName))
                    {
                        // 判断此属性是否有Setter      
                        if (!pi.CanWrite) continue;

                        object value = dr[tempName];
                        if (value != DBNull.Value)
                            pi.SetValue(t, value, null);
                    }
                }
                ts.Add(t);
            }
            return ts;
        }


        /// <summary>
        /// 这个方法有时转换会出现“System.NotSupportedException” : DataSet 不支持 System.Nullable<>。
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="collection"></param>
        /// <returns></returns>
        public static DataTable ConvertToDataTable<T>(IEnumerable<T> collection)
        {
            var props = typeof(T).GetProperties();
            var dt = new DataTable();
            dt.Columns.AddRange(props.Select(p => new DataColumn(p.Name, p.PropertyType)).ToArray());
            if (collection.Count() > 0)
            {
                for (int i = 0; i < collection.Count(); i++)
                {
                    ArrayList tempList = new ArrayList();
                    foreach (PropertyInfo pi in props)
                    {
                        object obj = pi.GetValue(collection.ElementAt(i), null);
                        tempList.Add(obj);
                    }
                    object[] array = tempList.ToArray();
                    dt.LoadDataRow(array, true);
                }
            }
            return dt;
        }




        public static DataTable ToDataTable<T>(IList<T> list)
        {
            return ToDataTable(list, null);
        }

        //将list转换成DataTable
        public static DataTable ToDataTable<T>(IList<T> list, params string[] propertyName)
        {
            List<string> propertyNameList = new List<string>();
            if (propertyName != null)
            {
                propertyNameList.AddRange(propertyName);
            }
            DataTable result = new DataTable();
            if (list.Count > 0)
            {
                PropertyInfo[] propertys = list[0].GetType().GetProperties();
                foreach (PropertyInfo pi in propertys)
                {
                    if (propertyNameList.Count == 0)
                    {
                        //if (DBNull.Value.Equals(pi.PropertyType))
                        //{
                        //   // pi.PropertyType = DateTime;
                        //}
                        Type colType = pi.PropertyType;
                        if (colType.IsGenericType && colType.GetGenericTypeDefinition() == typeof(Nullable<>))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }
                        result.Columns.Add(pi.Name, colType);
                        //result.Columns.Add(pi.Name, pi.PropertyType);
                    }
                    else
                    {
                        if (propertyNameList.Contains(pi.Name))
                        {
                            result.Columns.Add(pi.Name, pi.PropertyType);
                        }
                    }
                }
                for (int i = 0; i < list.Count; i++)
                {
                    ArrayList tempList = new ArrayList();
                    foreach (PropertyInfo pi in propertys)
                    {
                        if (propertyNameList.Count == 0)
                        {
                            object obj = pi.GetValue(list[i], null);
                            tempList.Add(obj);
                        }
                        else
                        {
                            if (propertyNameList.Contains(pi.Name))
                            {
                                object obj = pi.GetValue(list[i], null);
                                tempList.Add(obj);
                            }
                        }
                    }
                    object[] array = tempList.ToArray();
                    result.LoadDataRow(array, true);
                }
            }
            return result;
        }


        #region----DataTable转模型的另一种方法-----

        public static List<T> GetModelFromDB<T>(DataTable dt)
        {
            List<T> data = new List<T>();
            foreach (DataRow row in dt.Rows)
            {
                T item = GetItem<T>(row);
                data.Add(item);
            }
            return data;
        }

        /// <summary>
        /// 将DataRow转换成实体对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dr"></param>
        /// <returns></returns>
        public static T GetItem<T>(DataRow dr)
        {
            try
            {
                Type temp = typeof(T);
                T obj = Activator.CreateInstance<T>();
                foreach (DataColumn column in dr.Table.Columns)
                {
                    foreach (PropertyInfo pro in temp.GetProperties())
                    {
                        if (pro.Name.ToLower() == column.ColumnName.ToLower())
                        {
                            if (dr[column.ColumnName] == DBNull.Value)
                            {
                                pro.SetValue(obj, " ", null);
                                break;
                            }
                            else
                            {
                                pro.SetValue(obj, dr[column.ColumnName], null);
                                break;
                            }
                        }
                    }
                }
                return obj;
            }
           catch(Exception ex)
            {
                throw new Exception(ex.Message);
            }
        }

        #endregion

    }   

}

            //3.执行sql
            DataSet ds = AccessHelper.Query(strSql.ToString());
    
            DataTable dt = ds.Tables[0];
            //DataTable转List
            List<GoodsData> list = Bxlz.Common.ModelConvertHelper<GoodsData>.ConvertToModel(dt).ToList();

            foreach (var good in list)
            {
                string str = JsonConvert.SerializeObject(good);//把对象转换为JSON字符串
                Console.WriteLine(str);
            }
//List转DataTable
            DataTable dt1 = Bxlz.Common.ModelConvertHelper<GoodsData>.ToDataTable<GoodsData>(list);
            foreach (DataRow val in dt1.Rows)
            {
                Console.WriteLine("----={0}=---={1}=---={2}=---={3}=", val["uid"], val[1], val[2], val[4]);
            }