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; }
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