如果我的条件匹配，如何从另一个列表中选择项目？

如何解决如果我的条件匹配，如何从另一个列表中选择项目？

我有一个有关C＃列表的查询。

我有两种不同类型的列表（account和accountDescriptionHistory）。列表中同时显示accountID和accountdescription两列。

var account = new List<Account>();
var accountDescriptionHistory = new List<AccountDescriptionHistory>();

现在，我想根据以下条件准备结果列表。

如果accountID匹配，请从accountDescriptionHistory列表中选择一个帐户描述。
结果列表应为List（）;

类定义

public class Account
{

    /// <summary>
    /// The account number
    /// </summary>
    public virtual string AccountNumber { get; set; }

    /// <summary>
    /// The account's description
    /// </summary>
    public virtual string Description { get; set; }
}

帐户说明类别：

    public class AccountDescriptionHistory : EntityModel<AccountDescriptionHistory>
    {
        #region Public Properties

        /// <summary>
        /// The account description of an account that is valid for a specific date range
        /// </summary>
        public virtual string AccountDescription { get; set; }

        /// <summary>
        /// The account this AccountDescriptionHistory is associated with.
        /// </summary>
        public virtual Account Account { get; set; }
}

解决方法

您不清楚确切输出的问题。话虽如此。

给予

List<Account> accounts = new List<Account>
{ 
    new Account {AccountNumber = "1",Description = "Account 1"},new Account {AccountNumber = "2",Description = "Account 2"},new Account {AccountNumber = "4",Description = "Account 4"},};

List<AccountDescriptionHistory> accountHistories = new List<AccountDescriptionHistory>
{ 
    new AccountDescriptionHistory {AccountDescription = "History Account 1",Account = accounts[0] },new AccountDescriptionHistory {AccountDescription = "History Account 2",Account = accounts[1] },new AccountDescriptionHistory {AccountDescription = "History Account 3",Account = new Account {AccountNumber = "3",Description = "Account 3"} },};

我们想要使用accountHistories查找accounts中存在的所有AccountNumber，我们可以编写一个Where子句来查找所有这些内容：>

List<AccountDescriptionHistory> result = accountHistories
    .Where(x => accounts.Any(y => y.AccountNumber == x.Account.AccountNumber))
    .ToList();

如果您只想从结果中检索AccountDescription，则可以编写：

List<string> result = accountHistories
    .Where(x => accounts.Any(y => y.AccountNumber == x.Account.AccountNumber))
    .Select(x => x.AccountDescription)
    .ToList();

如果您希望将结果转换为Account中的描述，而将其转换为AccountDescriptionHistory，则可以执行以下操作：

List<Account> result = accountHistories
    .Where(x => accounts.Any(y => y.AccountNumber == x.Account.AccountNumber))
    .Select(x => new Account {AccountNumber = x.Account.AccountNumber,Description = x.AccountDescription})
    .ToList();

修改

您可以创建如下函数：

static Account WithDescriptionHistory(Account account,IEnumerable<AccountDescriptionHistory> accountHistories)
{
    AccountDescriptionHistory accountHistory = accountHistories.FirstOrDefault(x => x.Account.AccountNumber == account.AccountNumber);
    account.Description = accountHistory?.AccountDescription ?? account.Description;
    return account;
}

比像这样转换原始的account变量：

accounts = accounts
    .Select(x => WithDescriptionHistory(x,accountHistories))
    .ToList();

输出

History Account 1
History Account 2
Account 4

因此，根据您的评论，您需要此代码

foreach (var a in account)
{
    if (!accountDescriptionHistory.Any(x => x.accountID == a.accountID)) continue;
    a.Description = accountDescriptionHistory.FirstOrDefault(x => x.accountID == a.accountID).AccountDescription;
}

假设您具有以下两个类别：

public class A
{
    public int Id { get; set; }
}

public class B
{
    public int Id { get; set; }
    public string desc { get; set; }
}

您可以使用LINQ Join语句创建与第一个列表中的ID匹配的描述的列表

    List<A> one = new List<A>
    { 
        new A {Id = 1},new A {Id = 2} 
    };
    List<B> two = new List<B>
    { 
        new B {Id = 1,desc = "test"},new B {Id = 2,desc = "test two"} 
    };
    
    var result = one.Join(
        two,x => x.Id,y => y.Id,(x,y) => new {Id = x.Id,Desc = y.desc}
    ).ToList();

亲爱的阿米特，我希望这会有所帮助

public partial class TesterForm : Form
{
    List<Account> account = new List<Account>();
    List<AccountDescriptionHistory> accountDescriptionHistory = new List<AccountDescriptionHistory>();
    List<AccountDescriptionHistory> resultlist = new List<AccountDescriptionHistory>();

    public TesterForm()
    {
        InitializeComponent();
    }

    public class Account
    {
        public int accountID { get; set; }
        public string accountdescription { get; set; }
    }

    public class AccountDescriptionHistory
    {
        public int accountID { get; set; }
        public string accountdescription { get; set; }
    }

    private void button1_Click(object sender,EventArgs e)
    {
        Account accountmodel = new Account();
        accountmodel.accountID = 1;
        accountmodel.accountdescription = "desc1";
        account.Add(accountmodel);
        Account accountmodel1 = new Account();
        accountmodel1.accountID = 2;
        accountmodel1.accountdescription = "desc2";
        account.Add(accountmodel1);
        Account accountmodel3 = new Account();
        accountmodel3.accountID = 3;
        accountmodel3.accountdescription = "desc3";
        account.Add(accountmodel3);

        AccountDescriptionHistory accountdescmodel = new AccountDescriptionHistory();
        accountdescmodel.accountID = 3;
        accountdescmodel.accountdescription = "desc4";
        accountDescriptionHistory.Add(accountdescmodel);
        AccountDescriptionHistory accountdescmodel2 = new AccountDescriptionHistory();
        accountdescmodel2.accountID = 4;
        accountdescmodel2.accountdescription = "desc5";
        accountDescriptionHistory.Add(accountdescmodel2);
        AccountDescriptionHistory accountdescmodel3 = new AccountDescriptionHistory();
        accountdescmodel3.accountID = 5;
        accountdescmodel3.accountdescription = "desc6";
        accountDescriptionHistory.Add(accountdescmodel3);


    }

    private void button2_Click(object sender,EventArgs e)
    {
        foreach (Account item in account)
        {
            foreach (AccountDescriptionHistory item2 in accountDescriptionHistory)
            {
                if (item.accountID==item2.accountID)
                {
                    AccountDescriptionHistory history = new AccountDescriptionHistory();
                    history.accountID = item.accountID;
                    history.accountdescription = item2.accountdescription;
                    resultlist.Add(history);
                }
            }
        }
        comboBox1.DataSource = resultlist;
        comboBox1.DisplayMember = "accountdescription";
    }
}

我正在使用Visual Studio 2019窗体，您将需要两个按钮和一个组合按钮以查看我测试过的结果。添加到您的窗体combobox1，button1和button2。

如果我的条件匹配，如何从另一个列表中选择项目？

如何解决如果我的条件匹配，如何从另一个列表中选择项目？

解决方法

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