List<T> DataSet 转换

1.List-->DataSet

2.List<T>-->DataSet

3.DataSet-->List<T>

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
using System.Reflection;

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        
        
    }
    /// <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);//columnName Type
            }

            for (int i = 0; i < p_List.Count; i++)
            {
                ArrayList tempList = new ArrayList();    //一行数据的数组
                foreach (PropertyInfo pi in propertys)
                {
                    object obj = pi.GetValue(p_List[i], null);//p_List[i]是集合中的某一个对象，GetValue 返回其属性值
                    tempList.Add(obj);
                }
                object[] array = tempList.ToArray();
                _DataTable.LoadDataRow(array, true); //LoadDataRow 查找和更新特定行。 如果找不到任何匹配行，则使用给定值创建新行
            }
        }
        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(null时，表中字段全部转换，有数组时，只转换数组中和表字段都有的字段)</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); //AddRange 向……末尾，添加数组

        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 i = 0; i < p_Data.Rows.Count; i++)
        {
            T _t = (T)Activator.CreateInstance(typeof(T));//Activator.CreateInstrance C#在类工厂中动态创建类的实例
            PropertyInfo[] propertys = _t.GetType().GetProperties();
            foreach (PropertyInfo pi in propertys)
            {
                for (int j = 0; j < p_Data.Columns.Count; j++)
                {
                    // 属性与字段名称一致的进行赋值 
                    if (pi.Name.Equals(p_Data.Columns[j].ColumnName))
                    {
                        // 数据库NULL值单独处理 
                        if (p_Data.Rows[i][j] != DBNull.Value)
                            pi.SetValue(_t, p_Data.Rows[i][j], null);  //SetValue 将给定对象的属性值设置为给定值。
                        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);
    }
}

 +代码：

    /// <summary>
        /// DataTable 转换成Ilist<T>
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static IList<T> ConverToList(DataTable dt)
        {
            // 定义集合
            IList<T> ts = new List<T>();
            // 获得此模型的类型
            Type type = typeof(T);
            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)
                {
                    string 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 = null;
                        if (pi.PropertyType.FullName == "System.String")
                        {
                            value = dr[tempName].ToString();
                        }
                        else
                        {
                            value = dr[tempName];
                        }
                        if (value != DBNull.Value)
                        {
                            pi.SetValue(t, value, null);
                        }
                    }
                }
                ts.Add(t);
            }
            return ts;
        }

        /// <summary>
        /// Datatable 转换为Model
        /// 需要保证datatable里只有一条数据，如果是多条数据，会抛出异常
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static T ConverToModel(DataTable dt)
        {
            if (dt.Rows.Count != 1)
            {
                throw new Exception("传入的datatable中有" + dt.Rows.Count + "数据,而该参数只能有一条数据");
            }

            T t = new T();

            PropertyInfo[] propertys = t.GetType().GetProperties();
            foreach (PropertyInfo pi in propertys)
            {
                string 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 = null;
                    if (pi.PropertyType.FullName == "System.String")
                    {
                        value = dt.Rows[0][tempName].ToString();
                    }
                    else
                    {
                        value = dt.Rows[0][tempName];
                    }
                    if (value != DBNull.Value)
                    {
                        pi.SetValue(t, value, null);
                    }
                }
            }
            return t;
        }

 问题

Nullable转换

pi.SetValue(t, Convert.ChangeType(value, pi.PropertyType, CultureInfo.CurrentCulture), null);