C# 处理年月日提取时间

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace ExtractTime
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //--
            string[] strlist = {"年","月","日" };
            string strs = "日期:    2018年07月31日"; //xx年xx月xx日
            strs = textBox1.Text;


            var  test =  ff(strs);
            string[] temp = test.Split(new char[] { '#'}, StringSplitOptions.RemoveEmptyEntries);

            strs = strs.Replace(" ",""); //日期:2018年07月31日
            var cut = "";bool Mouthbl = false;
            //查询第一个年字所在位置
            for (int i=0;i<strs.Length;i++)
            {
                cut = strs.Substring(i,1); //截取一个字符
                if (cut.Contains("年")) //当前字符是年字
                {
                    //查找月字
                    for (int ii = i; ii < strs.Length; ii++)
                    {
                        cut = strs.Substring(ii, 1); //截取一个字符
                        if (cut.Contains("月")) //当前字符是月字
                        {
                            //包含月字
                            Mouthbl = true;
                            var x = i;
                            var y = ii;
                            if (y-x<=3&& y - x > 1) //年月,a年a月,aa年aa月
                            {
                                //截取字符串
                                if (i>=4)
                                {
                                    var year =  strs.Substring(i-4,4); //截取4个
                                    //验证该字符串是否是数字(略)
                                    var mouth = strs.Substring(ii - 2, 2).Replace("年",""); //截取月
                                    var day = "";
                                    //截取日
                                    if (strs.Length-(ii+1)>=3) //xx月xx日
                                    {
                                      day = strs.Substring(ii,3).Replace("月","");
                                    }
                                    textBox2.Text = year + mouth + day;
                                  
                                    break;

                                }
                            }
                           
                        }
                    }
                    if (Mouthbl)
                    {
                        break; //包含月
                    }
                }
            }




        }

        private void button2_Click(object sender, EventArgs e)
        {

            // Newmode.CompileDate = Convert.ToDateTime(CompileDate); //时间 字符串转时间
            textBox1.Text = "";
            textBox2.Text = "";
        }
        public string ff(string strs)
        {
            string result = "";

            strs = strs.Replace(" ", ""); //日期:2018年07月31日
            var cut = ""; bool Mouthbl = false;
            //查询第一个年字所在位置
            for (int i = 0; i < strs.Length; i++)
            {
                cut = strs.Substring(i, 1); //截取一个字符
                if (cut.Contains("年")) //当前字符是年字
                {
                    //查找月字
                    for (int ii = i; ii < strs.Length; ii++)
                    {
                        cut = strs.Substring(ii, 1); //截取一个字符
                        if (cut.Contains("月")) //当前字符是月字
                        {
                            //包含月字
                            Mouthbl = true;
                            var x = i;
                            var y = ii;
                            if (y - x <= 3 && y - x > 1) //年月,a年a月,aa年aa月
                            {
                                //截取字符串
                                if (i >= 4)
                                {
                                    var year = strs.Substring(i - 4, 4); //截取4个
                                    //验证该字符串是否是数字(略)
                                    var mouth = strs.Substring(ii - 2, 2).Replace("年", ""); //截取月
                                    if (mouth.Length == 1) //位数为1补0
                                    {
                                        mouth = "0" + mouth;
                                    }
                                    var day = "";
                                    //截取日
                                    if (strs.Length - (ii + 1) >= 3) //xx月xx日
                                    {
                                        day = strs.Substring(ii, 3).Replace("月", "");
                                        if (day.Length==1)////位数为1补0
                                        {
                                            day = "0" + day; 
                                        }
                                    }
                                    result = year+"#" + mouth + "#" + day;
                                    break;

                                }
                            }

                        }
                    }
                    if (Mouthbl)
                    {
                        break; //包含月
                    }
                }
            }
            return result;
        }
    }
}