Union擴(kuò)展方法需要兩個(gè)集合，并返回一個(gè)新集合，其中包含兩個(gè)集合中不同的元素?？聪旅娴膶?shí)例。
IList<string> strList1 = new List<string>() { "One", "Two", "three", "Four" };
IList<string> strList2 = new List<string>() { "Two", "THREE", "Four", "Five" };
var result = strList1.Union(strList2);
foreach(string str in result)
Console.WriteLine(str);One Two three THREE Four Five
Union擴(kuò)展方法不能為復(fù)雜類型的集合返回正確的結(jié)果。您需要實(shí)現(xiàn)IEqualityComparer接口，以便從Union方法中獲取正確的結(jié)果。
為 Student 類實(shí)現(xiàn)IEqualityComparer接口，如下所示：
public class Student
{
public int StudentID { get; set; }
public string StudentName { get; set; }
public int Age { get; set; }
}
class StudentComparer : IEqualityComparer<Student>
{
public bool Equals(Student x, Student y)
{
if (x.StudentID == y.StudentID && x.StudentName.ToLower() == y.StudentName.ToLower())
return true;
return false;
}
public int GetHashCode(Student obj)
{
return obj.StudentID.GetHashCode();
}
}現(xiàn)在，您可以在Union擴(kuò)展方法中傳遞上述StudentComparer類以獲得正確的結(jié)果：
示例：Uion運(yùn)算符 - C＃
IList<Student> studentList1 = new List<Student>() {
new Student() { StudentID = 1, StudentName = "John", Age = 18 } ,
new Student() { StudentID = 2, StudentName = "Steve", Age = 15 } ,
new Student() { StudentID = 3, StudentName = "Bill", Age = 25 } ,
new Student() { StudentID = 5, StudentName = "Ron" , Age = 19 }
};
IList<Student> studentList2 = new List<Student>() {
new Student() { StudentID = 3, StudentName = "Bill", Age = 25 } ,
new Student() { StudentID = 5, StudentName = "Ron" , Age = 19 }
};
var resultedCol = studentList1.Union(studentList2, new StudentComparer());
foreach(Student std in resultedCol)
Console.WriteLine(std.StudentName);John Steve Bill Ron
C # & VB.Net 查詢語法不支持聯(lián)合運(yùn)算符。但是，您可以對(duì)查詢變量使用 Union 方法，或者將整個(gè)查詢包裝到方括號(hào)中，然后調(diào)用 Union ()。