DataTable To List<T> DataTable Linq学习笔记

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LINQ 查询适用于实现的数据源 IEnumerable<T>接口或System.Query.IQueryable接口。

DataTable类默认是没有实现以上接口的。

所以要在DataTable中使用LINQ查询，需要调用一下AsEnumerable方法，返回一个EnumerableRowCollection<DataRow>集合。

实例如下所示：

using System;

using System.Collections.Generic;

using System.Data;

using System.Linq;

using System.Windows.Forms;

namespace DataTableToList

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private DataTable GetTable()

        {

            int[] id = { 4, 5, 1, 3, 2, 7, 6 };

            string[] name = { "Tom", "Jack", "Jime", "Lilei", "Jimo", "Koko", "Luoyi" };

            DataTable table = new DataTable("Student");

            table.Columns.Add("ID", typeof(int));

            table.Columns.Add("Name", typeof(string));

            for (int i = 0; i < id.Length; i++)

            {

                table.Rows.Add(new object[] { id[i], name[i] });

            }

            return table;

        }

        //order by

        private void button1_Click(object sender, EventArgs e)

        {

            DataTable dt = GetTable();

            var students = dt.AsEnumerable();

            //排序

            var result = students.OrderBy(x => x.Field<int>("ID"));

            //输出

            this.listBox1.Items.Clear();

            foreach (DataRow row in result)

            {

                this.listBox1.Items.Add("order by=="+row["ID"].ToString() + "==" + row["Name"].ToString());

            }

        }

        //where

        private void btnWhere_Click(object sender, EventArgs e)

        {

            DataTable dt = GetTable();

            var students = dt.AsEnumerable();

            //排序

            var result = students.Where(x => x.Field<int>("ID") > 3);

            //输出

            this.listBox1.Items.Clear();

            foreach (DataRow row in result)

            {

                this.listBox1.Items.Add("where=="+row["ID"].ToString() + "==" + row["Name"].ToString());

            }

        }

        private void btnToList_Click(object sender, EventArgs e)

        {

            DataTable dt = GetTable();

            var students = dt.AsEnumerable();

            List<Student> list = students.Select

                (

                   x => new Student

                    {

                        ID = x.Field<int>("ID"),

                        Name = x.Field<string>("Name")

                    }

                ).ToList();

            this.listBox1.Items.Clear();

            foreach (Student item in list)

            {

                this.listBox1.Items.Add("tolist=="+item.ID + "==" + item.Name);

            }

        }

    }

    public class Student

    {

        public int ID { get; set; }

        public string Name { get; set; }

    }

}

运行效果如下：

方式二：

/// <summary>

        /// DataTable转成List

        /// </summary>

        /// <typeparam name="T"></typeparam>

        /// <param name="dt"></param>

        /// <returns></returns>

        public static List<T> DataTableToList<T>(this DataTable dt)

        {

            var list = new List<T>();

            var plist = new List<PropertyInfo>(typeof(T).GetProperties());

            foreach (DataRow item in dt.Rows)

            {

                T s = Activator.CreateInstance<T>();

                for (int i = 0; i < dt.Columns.Count; i++)

                {

                    PropertyInfo info = plist.Find(p => p.Name == dt.Columns[i].ColumnName);

                    if (info != null)

                    {

                        try

                        {

                            if (!Convert.IsDBNull(item[i]))

                            {

                                object v = null;

                                if (info.PropertyType.ToString().Contains("System.Nullable"))

                                    v = Convert.ChangeType(item[i], Nullable.GetUnderlyingType(info.PropertyType));

                                else v = Convert.ChangeType(item[i], info.PropertyType);

                                info.SetValue(s, v, null);

                            }

                        }

                        catch (Exception ex)

                        {

                            throw new Exception("字段[" + info.Name + "]转换出错," + ex.Message);

                        }

                    }

                }

                list.Add(s);

            }

            return list;

        }