using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Web;

/// <summary>
/// DataTableEx 的摘要说明
/// </summary>
public static class DataTableEx
{
    public static List<T> ToList<T>(this DataTable dt) where T : new()
    {
        List<T> ts = new List<T>();
        foreach (DataRow dr in dt.Rows)
        {
            T t = new T();
            foreach (var c in dt.Columns)
            {
                object value = dr[c.ToString()];
                if (value != DBNull.Value)
                {
                    var p = t.GetType().GetProperty(c.ToString());
                    if (p != null)
                    {
                        p.SetValue(t, ConvertHelper.ChangeType(value, p.PropertyType), null);
                    }
                }
            }
            ts.Add(t);
        }
        return ts;
    }


    public static List<T> ConvertTo<T>(DataTable datatable) where T : new()
    {
        var temp = new List<T>();
        try
        {
            var columnsNames = (from DataColumn dataColumn in datatable.Columns select dataColumn.ColumnName).ToList();
            temp = datatable.AsEnumerable().ToList().ConvertAll<T>(row => GetObject<T>(row, columnsNames));
            return temp;
        }
        catch
        {
            return temp;
        }
    }


    private static T GetObject<T>(DataRow row, List<string> columnsName) where T : new()
    {
        T obj = new T();
        try
        {
            string columnname = "";
            PropertyInfo[] Properties = typeof(T).GetProperties();
            foreach (PropertyInfo objProperty in Properties)
            {
                columnname = columnsName.Find(name => name.ToLower() == objProperty.Name.ToLower());
                if (!string.IsNullOrEmpty(columnname))
                {
                    var value = row[columnname];
                    if (!string.IsNullOrEmpty(value.ToString()))
                    {
                        Type type;
                        type = Nullable.GetUnderlyingType(objProperty.PropertyType) ?? objProperty.PropertyType;
                        objProperty.SetValue(obj,
                                                                     type == value.GetType()
                                                                         ? Convert.ChangeType(value, type)
                                                                         : System.Enum.ToObject(type, value), null);
                    }
                }
            }
            return obj;
        }
        catch (Exception exception)
        {
            return obj;
        }
    }


    /// <summary>
    /// 单字段值
    /// </summary>
    /// <returns></returns>
    public static List<string> ToList(this DataTable dt)
    {
        List<string> ts = new List<string>();
        foreach (DataRow dr in dt.Rows)
        {
            foreach (var c in dt.Columns)
            {
                object value = dr[c.ToString()];
                if (value != DBNull.Value)
                {
                    ts.Add(value.ToString());
                }
            }
        }
        return ts;
    }


    public static T ToData<T>(this DataTable dt) where T : new()
    {
        if (dt.Rows.Count > 1)
        {
            throw new Exception("");
        }
        List<T> ts = new List<T>();
        foreach (DataRow dr in dt.Rows)
        {
            T t = new T();
            foreach (var c in dt.Columns)
            {
                object value = dr[c.ToString()];
                if (value != DBNull.Value)
                {
                    var p = t.GetType().GetProperty(c.ToString());
                    if (p != null)
                    {
                        p.SetValue(t, ConvertHelper.ChangeType(value, p.PropertyType), null);
                    }
                }
            }
            return t;
        }
        return default(T);
    }

    public static void FillData<T>(this DataTable dt, ref T t) where T : new()
    {
        if (dt.Rows.Count > 1)
        {
            throw new Exception("");
        }
        foreach (DataRow dr in dt.Rows)
        {

            foreach (var c in dt.Columns)
            {
                object value = dr[c.ToString()];
                if (value != DBNull.Value)
                {
                    var p = t.GetType().GetProperty(c.ToString());
                    if (p != null)
                    {
                        p.SetValue(t, ConvertHelper.ChangeType(value, p.PropertyType), null);
                    }
                }
            }
        }
    }

    /// <summary>
    /// list转化为table
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="entitys"></param>
    /// <returns></returns>
    public static DataTable ListToDataTable<T>(List<T> entitys)
    {

        //检查实体集合不能为空
        if (entitys == null || entitys.Count < 1)
        {
            return new DataTable();
        }

        //取出第一个实体的所有Propertie
        Type entityType = entitys[0].GetType();
        PropertyInfo[] entityProperties = entityType.GetProperties();

        //生成DataTable的structure
        //生产代码中，应将生成的DataTable结构Cache起来，此处略
        DataTable dt = new DataTable("dt");
        for (int i = 0; i < entityProperties.Length; i++)
        {
            //dt.Columns.Add(entityProperties[i].Name, entityProperties[i].PropertyType);
            dt.Columns.Add(entityProperties[i].Name);
        }

        //将所有entity添加到DataTable中
        foreach (object entity in entitys)
        {
            //检查所有的的实体都为同一类型
            if (entity.GetType() != entityType)
            {
                throw new Exception("要转换的集合元素类型不一致");
            }
            object[] entityValues = new object[entityProperties.Length];
            for (int i = 0; i < entityProperties.Length; i++)
            {
                entityValues[i] = entityProperties[i].GetValue(entity, null);

            }
            dt.Rows.Add(entityValues);
        }
        return dt;
    }

    /// <summary>
    /// 查询指定条数分页
    /// </summary>
    /// <returns></returns>
    public static DataTable GetPageToTable(DataTable dt, int StartNum, int EndNum)
    {
        //0页代表每页数据，直接返回
        if (EndNum == 0) return dt;
        //数据源为空返回空DataTable
        if (dt == null) return new DataTable();

        DataTable newdt = dt.Copy();
        newdt.Clear();//copy dt的框架

        if (StartNum >= dt.Rows.Count)
            return newdt;//源数据记录数小于等于要显示的记录，直接返回dt

        if (EndNum > dt.Rows.Count)
            EndNum = dt.Rows.Count;
        for (int i = StartNum; i <= EndNum - 1; i++)
        {
            DataRow newdr = newdt.NewRow();
            DataRow dr = dt.Rows[i];
            foreach (DataColumn column in dt.Columns)
            {
                newdr[column.ColumnName] = dr[column.ColumnName];
            }
            newdt.Rows.Add(newdr);
        }
        return newdt;
    }
}
public static class ConvertHelper
{
    public static object ChangeType(object obj, Type conversionType)
    {
        return ChangeType(obj, conversionType, System.Threading.Thread.CurrentThread.CurrentCulture);
    }

    public static object ChangeType(object obj, Type conversionType, IFormatProvider provider)
    {

        #region Nullable
        Type nullableType = Nullable.GetUnderlyingType(conversionType);
        if (nullableType != null)
        {
            if (obj == null)
            {
                return null;
            }
            return Convert.ChangeType(obj, nullableType, provider);
        }
        #endregion
        if (typeof(System.Enum).IsAssignableFrom(conversionType))
        {
            return Enum.Parse(conversionType, obj.ToString());
        }
        return Convert.ChangeType(obj, conversionType, provider);
    }


    /// <summary>
    /// 分页
    /// </summary>
    /// <returns></returns>
    public static List<T> PageList<T>(List<T> list, out int total, int pageIndex = 1, int pageSize = 10)
    {
        pageIndex = pageIndex - 1;
        total = 0;
        if (list == null || list.Count == 0)
            return list;
        total = list.Count;
        int startIndex = pageIndex * pageSize;
        if (startIndex + pageSize > list.Count)
        {
            pageSize = list.Count - startIndex;
        }

        if (pageSize <= 0) return new List<T>();

        return list.GetRange(startIndex, pageSize);
    }
}