DataSet和List 泛型之间互相转换 (转载, 作者写的很好)

时间:2024-05-30 19:34:32

/DataSet与泛型集合间的互相转换

//利用反射机制将DataTable的字段与自定义类型的公开属性互相赋值。
//注意:从DataSet到IList<T>的转换,自定义类型的公开属性必须与DataTable中的字段名称
//一致,才能到达想要的结果。建议DataTable的定义从数据库来,自定义类型用O/R Mapping的方式获得。
//代码说明
/// <summary>
/// 泛型集合与DataSet互相转换
/// </summary>
using System.Data;
using System.Reflection;
using System.Collections;
using System.Collections.Generic;
using System;
public class IListDataSet
{
    /// <summary>
    /// 集合装换DataSet
    /// </summary>
    /// <param name="list">集合</param>
    /// <returns></returns>
    /// 2008-08-01 22:08 HPDV2806
    public static DataSet ToDataSet(IList p_List)
    {
        DataSet result = new DataSet();
        DataTable _DataTable = new DataTable();
        if (p_List.Count > 0)
        {
            PropertyInfo[] propertys = p_List[0].GetType().GetProperties();
            foreach (PropertyInfo pi in propertys)
            {
                _DataTable.Columns.Add(pi.Name, pi.PropertyType);
            }
            for (int i = 0; i < p_List.Count; i++)
            {
                ArrayList tempList = new ArrayList();
                foreach (PropertyInfo pi in propertys)
                {
                    object obj = pi.GetValue(p_List[i], null);
                    tempList.Add(obj);
                }
                object[] array = tempList.ToArray();
                _DataTable.LoadDataRow(array, true);
            }
        }
        result.Tables.Add(_DataTable);
        return result;
    }
    /// <summary>
    /// 泛型集合转换DataSet
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="list">泛型集合</param>
    /// <returns></returns>
    /// 2008-08-01 22:43 HPDV2806
    public static DataSet ToDataSet<T>(IList<T> list)
    {
        return ToDataSet<T>(list, null);
    }
    /// <summary>
    /// 泛型集合转换DataSet
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="p_List">泛型集合</param>
    /// <param name="p_PropertyName">待转换属性名数组</param>
    /// <returns></returns>
    /// 2008-08-01 22:44 HPDV2806
    public static DataSet ToDataSet<T>(IList<T> p_List, params string[] p_PropertyName)
    {
        List<string> propertyNameList = new List<string>();
        if (p_PropertyName != null)
            propertyNameList.AddRange(p_PropertyName);
        DataSet result = new DataSet();
        DataTable _DataTable = new DataTable();
        if (p_List.Count > 0)
        {
            PropertyInfo[] propertys = p_List[0].GetType().GetProperties();
            foreach (PropertyInfo pi in propertys)
            {
                if (propertyNameList.Count == 0)
                {
                    // 没有指定属性的情况下全部属性都要转换
                    _DataTable.Columns.Add(pi.Name, pi.PropertyType);
                }
                else
                {
                    if (propertyNameList.Contains(pi.Name))
                        _DataTable.Columns.Add(pi.Name, pi.PropertyType);
                }
            }
            for (int i = 0; i < p_List.Count; i++)
            {
                ArrayList tempList = new ArrayList();
                foreach (PropertyInfo pi in propertys)
                {
                    if (propertyNameList.Count == 0)
                    {
                        object obj = pi.GetValue(p_List[i], null);
                        tempList.Add(obj);
                    }
                    else
                    {
                        if (propertyNameList.Contains(pi.Name))
                        {
                            object obj = pi.GetValue(p_List[i], null);
                            tempList.Add(obj);
                        }
                    }
                }
                object[] array = tempList.ToArray();
                _DataTable.LoadDataRow(array, true);
            }
        }
        result.Tables.Add(_DataTable);
        return result;
    }
    /// <summary>
    /// DataSet装换为泛型集合
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="p_DataSet">DataSet</param>
    /// <param name="p_TableIndex">待转换数据表索引</param>
    /// <returns></returns>
    /// 2008-08-01 22:46 HPDV2806
    public static IList<T> DataSetToIList<T>(DataSet p_DataSet, int p_TableIndex)
    {
        if (p_DataSet == null || p_DataSet.Tables.Count < 0)
            return null;
        if (p_TableIndex > p_DataSet.Tables.Count - 1)
            return null;
        if (p_TableIndex < 0)
            p_TableIndex = 0;
        DataTable p_Data = p_DataSet.Tables[p_TableIndex];
        // 返回值初始化
        IList<T> result = new List<T>();
        for (int j = 0; j < p_Data.Rows.Count; j++)
        {
            T _t = (T)Activator.CreateInstance(typeof(T));
            PropertyInfo[] propertys = _t.GetType().GetProperties();
            foreach (PropertyInfo pi in propertys)
            {
                for (int i = 0; i < p_Data.Columns.Count; i++)
                {
                    // 属性与字段名称一致的进行赋值
                    if (pi.Name.Equals(p_Data.Columns[i].ColumnName))
                    {
                        // 数据库NULL值单独处理
                        if (p_Data.Rows[j][i] != DBNull.Value)
                            pi.SetValue(_t, p_Data.Rows[j][i], null);
                        else
                            pi.SetValue(_t, null, null);
                        break;
                    }
                }
            }
            result.Add(_t);
        }
        return result;
    }
    /// <summary>
    /// DataSet装换为泛型集合
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="p_DataSet">DataSet</param>
    /// <param name="p_TableName">待转换数据表名称</param>
    /// <returns></returns>
    /// 2008-08-01 22:47 HPDV2806
    public static IList<T> DataSetToIList<T>(DataSet p_DataSet, string p_TableName)
    {
        int _TableIndex = 0;
        if (p_DataSet == null || p_DataSet.Tables.Count < 0)
            return null;
        if (string.IsNullOrEmpty(p_TableName))
            return null;
        for (int i = 0; i < p_DataSet.Tables.Count; i++)
        {
            // 获取Table名称在Tables集合中的索引值
            if (p_DataSet.Tables[i].TableName.Equals(p_TableName))
            {
                _TableIndex = i;
                break;
            }
        }
        return DataSetToIList<T>(p_DataSet, _TableIndex);
    }
}
/*****************
使用范围
1. 可以用在业务层中数据获取,获取DataSet的同时也可以转为IList集合为调用者所使用。
2. 在WebServices中传输自定义类型使用,即传递参数都用DataSet类型(WebServices直接支持的数据类型),在使用前将其转换为IList来使用。
 * ******************************/