根据条件并行调用方法答案

【问题标题】：Invoke methods in parallel based on condition根据条件并行调用方法
【发布时间】：2019-02-23 07:37:58
【问题描述】：

public IList<Student> GetStudentList()
{
    var students = new List<Student>();
    if(getOtherSchoolStudents)
    {
        var otherSchoolStudents  = GetOtherSchoolStudents();
        students.AddRange(otherSchoolStudents);
    }
    var currentSchoolStudents = GetCurrentSchoolStudents();
    students.AddRange(currentSchoolStudents)
    return students;
}

这里当getOtherSchoolStudents 是true 时，我想并行运行GetOtherSchoolStudents() 和GetCurrentSchoolStudents() 方法。我知道我可以将GetCurrentSchoolStudents() 移到条件范围内并同时运行，如下所示

public IList<Student> GetStudentList()
{
    var students = new List<Student>();
    if(getOtherSchoolStudents)
    {
        var otherSchoolStudents  = GetOtherSchoolStudents(); // run in parallel
        var currentSchoolStudents = GetCurrentSchoolStudents(); // run in parallel
        students.AddRange(otherSchoolStudents);
        students.AddRange(currentSchoolStudents)
    }
    else
    {
        var currentSchoolStudents = GetCurrentSchoolStudents(); 
        students.AddRange(currentSchoolStudents);
    }
    return students;
}

还有其他方法吗？

【问题讨论】：

标签： c# asynchronous parallel-processing async-await task-parallel-library

【解决方案1】：

最简单的方法可能是并行调用两个 get 操作：

public IList<Student> GetStudentList()
{
    List<Student> currentSchoolStudents;
    List<Student> otherSchoolStudents; 

    Parallel.Invoke(
    { currentSchoolStudents = GetCurrentSchoolStudents(); }
    { otherSchoolStudents = getOtherSchoolStudents 
                          ? GetOtherSchoolStudents() 
                          : new List<Student>(); }
    );

    var students = new List<Student>();
    students.AddRange(otherSchoolStudents);
    students.AddRange(currentSchoolStudents)
    return students;
}

这假设您的操作返回 List<Student>，如果它们返回其他内容，例如 Student[]，您需要相应地更改类型。

【讨论】：