c# - 检查 session 中是否已存在数组

Question

在 Visual C# 中，如何检测 Session 中是否已存在数组？该网站有一个文本框，你可以写一个名字。当您单击“单击”按钮时，它会在标签中添加名称。假设我添加了相同的名称，它应该在标签中显示一条消息，如“名称已存在!”。我应该怎么办？我读到了“包含”方法，但对我来说效果不佳。我犯了什么错误？

下面的代码是:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    protected void btnClick_Click(object sender, EventArgs e)
    {
        if (Session["listOfCharacters"] == null) 
        {
            Session.Add("listOfCharacters", new List<Character>());
        }

        List<Character> listOfCharacters = (List<Character>)Session["listOfCharacters"];

        listOfCharacters.Add(new Character() { name = txtName.Text});

        lblShow.Text = "";

        foreach (Character item in listOfCharacters)
        {
            lblShow.Text += "Name: " + item.name + "<br />";

        //if (listOfCharacters.Contains(Session["listOfCharacters"]))
        //{
        //    lblShow.Text = "Exists";
        //}
        }
    }
}

相信我，我花了几个小时甚至几天的时间，但还没有找到解决方案。

Answer 1

您可以编写 LINQ 查询来检查该项目是否存在于列表中

例如

private string _listofcharacters = "listOfCharacters";
protected void Button1_Click(object sender, EventArgs e)
{
    if (Session[_listofcharacters] == null)
    {
        Session.Add(_listofcharacters, new List<Character>());
    }

    List<Character> listOfCharacters = (List<Character>)Session[_listofcharacters];

    lblShow.Text = "";

    var check = from p in listOfCharacters
                where p.Name.ToLower().Contains(txtName.Text.ToLower())
                select p;

    if (check.Count() == 0)
    {
        listOfCharacters.Add(new Character() { Name = txtName.Text });

        foreach (Character item in listOfCharacters)
        {
            lblShow.Text += "Name: " + item.Name + "<br />";
        }
    }
    else
    {
        lblShow.Text = "Name already exists!";
    }
}