只有一个相等运算符:SequenceEqual。SequenceEqual方法检查两个集合中的元素数量,每个元素的值和元素的顺序是否相等。
如果集合包含原始数据类型的元素,则它将比较元素的值和数量,而具有复杂类型元素的集合将检查对象的引用。因此,如果对象具有相同的引用,则将它们视为相等,否则将其视为不相等。
下面的示例演示了带有原始数据类型集合的SequenceEqual方法。
IList<string> strList1 = new List<string>(){"One", "Two", "Three", "Four", "Three"}; IList<string> strList2 = new List<string>(){"One", "Two", "Three", "Four", "Three"}; bool isEqual = strList1.SequenceEqual(strList2); // 返回true Console.WriteLine(isEqual);
True
如果元素的顺序不同,则SequenceEqual()方法返回false。
IList<string> strList1 = new List<string>(){"One", "Two", "Three", "Four", "Three"}; IList<string> strList2 = new List<string>(){ "Two", "One", "Three", "Four", "Three"}; bool isEqual = strList1.SequenceEqual(strList2); // 返回false Console.WriteLine(isEqual);
false
SequenceEqual扩展方法检查两个对象的引用,以确定两个序列是否相等。这可能会给出错误的结果。看以下示例:
Student std = new Student() { StudentID = 1, StudentName = "Bill" }; IList<Student> studentList1 = new List<Student>(){ std }; IList<Student> studentList2 = new List<Student>(){ std }; bool isEqual = studentList1.SequenceEqual(studentList2); // 返回true Student std1 = new Student() { StudentID = 1, StudentName = "Bill" }; Student std2 = new Student() { StudentID = 1, StudentName = "Bill" }; IList<Student> studentList3 = new List<Student>(){ std1}; IList<Student> studentList4 = new List<Student>(){ std2 }; isEqual = studentList3.SequenceEqual(studentList4);// 返回false
在上面的示例中,studentList1和studentList2包含相同的学生对象std。因此studentList1.SequenceEqual(studentList2)返回true。但是,stdList1和stdList2包含两个单独的学生对象std1和std2。所以现在,即使std1和std2包含相同的值,stdList1.SequenceEqual(stdList2)也将返回false。
要比较两个复杂类型(引用类型或对象)集合的值,需要实现IEqualityComperar <T>接口,如下所示。
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.GetHashCode(); } }
现在,您可以使用SequenceEqual扩展方法中的上述StudentComparer类作为第二个参数来比较值:
示例:C#使用SequenceEqual比较对象类型元素
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 = 4, StudentName = "Ram" , Age = 20 } , new Student() { StudentID = 5, StudentName = "Ron" , Age = 19 } }; IList<Student> studentList2 = 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 = 4, StudentName = "Ram" , Age = 20 } , new Student() { StudentID = 5, StudentName = "Ron" , Age = 19 } }; // 以下返回true bool isEqual = studentList1.SequenceEqual(studentList2, new StudentComparer());
SequenceEqual方法比较项目数及其原始数据类型的值。
SequenceEqual方法比较对象对复杂数据类型的引用。
使用IEqualityComparer类可通过SequenceEqual方法比较两个复杂类型的集合。