C#集合多种实现

最新推荐文章于 2021-10-14 12:27:41 发布

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本文主要探讨了C#中集合的各种实现方式，通过代码实例进行详细讲解，帮助读者深入理解C#集合的使用。

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1.代码练习

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            //================根据value获取key========
            Dictionary<int, string> dic = new Dictionary<int, string>();
            dic.Add(1, "A");
            dic.Add(2, "B");
            dic.Add(3, "C");

            string v = "C";
            int k = 0;
            //C#
            foreach (KeyValuePair<int,string> item in dic)
            {
                if (item.Value.Contains(v))
                    k = item.Key;
            }

            //Lambda
           var keys=dic.Where(i => i.Value == v).Select(i => i.Key);
            foreach (var ik in keys)
            {
                k = ik;
            }

            //Lambda
            k = dic.FirstOrDefault(item => item.Value.Contains(v)).Key;

            //Linq
            k = (from item in dic
                 where item.Value.Contains(v)
                 select item.Key).FirstOrDefault();



            //================获取DataTable选择第一行某一列值========
            CustomerEntity ct = new CustomerEntity();
            var table = ct.Customer();
            var row = (from r in table.Rows.Cast<DataRow>()
                       select r).FirstOrDefault();
            string CustomerName = row.Field<string>("CustomerName");


            //
             CustomerName = (from r in table.Rows.Cast<DataRow>()
            select r.Field<string>("CustomerName")).FirstOrDefault();

            CustomerName = table.Rows[0][1].ToString();

            CustomerName = table.Rows[0]["CustomerName"].ToString();

             
            Console.WriteLine(table.Rows[0]["CustomerName"].ToString());
        }
    }

    public class CustomerEntity
    {
        public DataTable Customer()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("CustomerID", typeof(int)));
            dt.Columns.Add(new DataColumn("CustomerName", typeof(string)));
            DataRow dr = dt.NewRow();
            dr["CustomerID"] = 9;
            dr["CustomerName"] = "张三";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["CustomerID"] = 10;
            dr["CustomerName"] = "李四";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["CustomerID"] = 13;
            dr["CustomerName"] = "王五";
            dt.Rows.Add(dr);

            return dt;
        }

        public int CustomerID { get; set; }

        public string CustomerName { get; set; }
    }
}