比较2个单独列表中的2个属性

Question

我有2个单独的课程列表。 1个列表是当前课程，另一个列表是已过滤课程。我想比较列表，如果课程存在或不存在，我想将FilteredCourse列表上的布尔值标记为true或false。下面是示例代码。

var currentCourses = new List<Course>
        {
            new Course{CourseNumber = "101", CourseSubject = "ART"},
            new Course{CourseNumber = "201", CourseSubject = "BIO"},
            new Course{CourseNumber = "301", CourseSubject = "CHEM"},
            new Course{CourseNumber = "401", CourseSubject = "CPSC"}
        };

        var filteredCourses = new List<Course>
        {
            new Course{CourseNumber = "101", CourseSubject = "ART"},
            new Course{CourseNumber = "401", CourseSubject = "CPSC"},
            new Course{CourseNumber = "501", CourseSubject = "DANC"},
            new Course{CourseNumber = "701", CourseSubject = "HIST"}
        };

我尝试过：

foreach (var course in currentCourses)
        {
            foreach (var filteredCourse in filteredCourses)
            {
                if ((filteredCourse.CourseNumber === course.CourseNumber) && (filteredCourse.CourseSubject === course.CourseSubject))
                {
                    filteredCourse.AlreadyExists = true;
                }
                else
                {
                    filteredCourse.AlreadyExists = false;
                }
            }
        }

Answer 1

您应该在开始时将所有标志设置为false，然后运行循环并仅在找到匹配项时才设置true标志。如果您运行当前的代码，它将遍历所有课程，并且如果匹配的课程不是最后一门课程，则即使将其设置为true，该标志也将始终设置为false。

找到匹配项后，您也可以跳出循环。

类似这样：

foreach (var filteredCourse in filteredCourses)
    filteredCourse.AlreadyExists = false;

foreach (var course in currentCourses)
{
    foreach (var filteredCourse in filteredCourses)
    {
        if ((filteredCourse.CourseNumber == course.CourseNumber) && (filteredCourse.CourseSubject == course.CourseSubject))
        {
            filteredCourse.AlreadyExists = true;
            break;
        }
    }
}

Answer 2

您可以使用LINQ：

foreach (var f in filteredCourses)
{
  f.AlreadyExists = currentCourses.Any(c => (c.CourseNumber == f.CourseNumber 
    && c.CourseSubject == f.CourseSubject));
}