Unity (C#) Linq operation

• Query by condition: usage of from in where select

 // 例如:获取某班级所有男生成绩总和
 int scoreSum = (from student in classStudents
				 where student.gender == "男"  // where：查询条件
				 select student.score).Sum(); // select：选择对象
// 找出班级内所有男生
 boys=(from stud classStudents where stud.gender == "男" select stud).ToList();

• random order:

// 给集合、数组按照某种类型，随机排序
mlist = mlist.Where(it => it.type == 1).OrderBy(x => Guid.NewGuid()).ToList();
// 按照指定类型，随机取出集合中的某个元素
randomItem = mlist.Where(it => it.type == 1).OrderBy(x => Guid.NewGuid()).First();

• Determine whether there is an object in a collection that satisfies the condition:

// 例如：三班学生中中有没有叫"小明"的同学
// 方式1：
bool result1 = classThreeStudent.Exists(student => student.name == "小明");
// 方式2：建议使用Exists判断，元素多了，Any判断效率不高。
bool result2 = classThreeStudent.Any(student => student.name == "小明");

• Find objects based on criteria:

// 方式1：
Role xiaoMing = roleList.Find(r => r.name == "小明");

// 方式2：
int index = roleList.FindIndex(r => r.name == "小明");
if (index == -1) {
    
    
    // 没有找到叫小明的角色
} else {
    
    
    Role xiaoMing = roleList[index];
}

// 等等...