C#LINQ-回圈串列

我在下面有一個測驗 LINQ 串列

List<test> test=new List<test>();
test.Add(new test("Bakery","[email protected]","Donut"));
test.Add(new test("Bakery","[email protected]","Bagel"));
test.Add(new test("Bakery","[email protected]","Cake"));
test.Add(new test("Produce","[email protected]","Apple"));
test.Add(new test("Dairy","[email protected]","Milk"));
test.Add(new test("Dairy","[email protected]","Yogurt"));

有些部門有超過 1 個專案。如何遍歷串列并向每個部門/電子郵件地址發送 1 封電子郵件和專案。向 [email protected] 發送 1 封電子郵件，其中包含 Donut、Bagel、Cake。發送 1 封電子郵件至 [email protected]，正文中包含 Apple。向[email protected] 發送1 封電子郵件，其中包含牛奶、酸奶

我不需要電子郵件部分的幫助，只需要幫助遍歷串列并獲取每個部門的專案。非常感謝！！！

uj5u.com熱心網友回復：

我認為，您可以將分組用于任務。

var groups = test.GroupBy(x => x.Email);
foreach (var group in groups)
{
  var email = group.Key; // Exactly the property from GroupBy
  var goods = group.Select(x => x.Good); // Donut, Bagel, Cake...
  var body = string.Join(", ", goods);

  // Now you can send the email with body containing "Donut, Bagel. Cake"
}

group變數的每個實體都包含Key屬性和集合中分組項的test集合。

因此，您可以將group與 之類的方法一起使用，也可以將其Select與foreach運算子一起使用。

uj5u.com熱心網友回復：

List<test> test=new List<test>();
test.Add(new test("Bakery","[email protected]","Donut"));
test.Add(new test("Bakery","[email protected]","Bagel"));
test.Add(new test("Bakery","[email protected]","Cake"));
test.Add(new test("Produce","[email protected]","Apple"));
test.Add(new test("Dairy","[email protected]","Milk"));
test.Add(new test("Dairy","[email protected]","Yogurt"));

foreach (var group in test.GroupBy(x=> x.Department))
{
    var department = group.Key;
    var email = group.First().Email;
    var body = string.Join(", ", group.Select(x => x.Product));

    SendMail(email, department, body);
}

uj5u.com熱心網友回復：

如果您想對（專案）進行分組GroupBy，讓我們（按Department和Address）。首先，讓我們準備資料：

var emails = test
  .GroupBy(item => (department : item.Department, address : item.Address),
           item => item.Item)
  .Select(group => (department : group.Key.department,
                    address    : group.Key.address,
                    body       : string.Join(", ", group.Distinct().OrderBy(item => item))));

然后我們準備發送郵件：

foreach (var letter in emails)
  SendEmail(letter.address, letter.deparment, letter.body);

uj5u.com熱心網友回復：

你確定所有tests部門Bakery的人都有相同的電子郵件地址嗎？或者可能是（例如，由于輸入錯誤）某些面包店有不同的電子郵件地址？

如果所有 Bakeries 都具有相同的地址，那么您可以使用Enumerable.GroupBy的多載之一來創建具有相同部門的測驗組。然后為每個組獲取該組中第一個測驗的電子郵件（或任何其他，無論如何它們都是相同的）。使用帶引數的多載resultselector來指定結果

class Test
{
    public string Department {get; set;}
    public string EmailAddress {get; set;}
    ... // other properties
}

IEnumerable<Test> myTests = ...

var departmentsEmailAddresses = myTests.GroupBy(

    // make groups of test that have the same value for Department
    test => test.Department,

    // parameter resultSelector: for every Department name and all Tests that have
    // this value for Department name, make one new object:
    (department, testsWithThisValueForDepartment) => new
    {
        // if desired: remember the department name
        Department = department,

        // to get the e-mail address, take the first test.
        // BTW: all tests in this group will have the same e-mail address
        Email = testsWithThisValueForDepartment.Select(test => test.EmailAddress)
                                               .FirstOrDefault(),
    })

換句話說：對于所有測驗，創建一組具有相同屬性值的測驗Department。每個小組至少有一個測驗。Department從每個組中，獲取該組中所有測驗的共同值。此外，在該組中進行測驗，并選擇 的值EmailAddress。僅對組中的第一個測驗執行此操作。

結果將是一系列的組合[Department, Email]

標籤：C＃林克

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