C# 为什么无法通过IndexOf（）找到CheckedListBox中存在的项？

我有以下代码：

if (currentWeekSaved)
{
    DateTime currentWeek = Convert.ToDateTime(comboBoxWeekToSchedule.SelectedValue);
    AssignmentHistory ah = AYttFMConstsAndUtils.AssignmentHistList
        .FirstOrDefault(i => i.WeekOfAssignment == currentWeek && i.TalkType == BIBLE_READING_TALK_TYPE);
    if (ah != null)
    {
        var assignedStudentFirstname = AYttFMConstsAndUtils.GetStudentFirstNameForID(ah.StudentID_FK);
        var assignedStudentLastname = AYttFMConstsAndUtils.GetStudentLastNameForID(ah.StudentID_FK);
        assignedStudent = new Student() {FirstName = assignedStudentFirstname, LastName = assignedStudentLastname, StudentID = ah.StudentID_FK};
    }
}
List<Student> BRStudents =
    AYttFMConstsAndUtils.StudentsList.Where(h => h.EnrolledInAYttFM)
        .Where(i => i.RecommendedNextTalkTypeID.Equals(BIBLE_READING_TALK_TYPE))
        .OrderBy(j => j.WeekOfLastAssignment)
        .ToList();
if (null != assignedStudent)
{
    // If exists in list, remove it first, and then add it back at the top
    //int assignedStudentIndex = BRStudents.IndexOf(assignedStudent);
    int assignedStudentIndex = checkedListBoxBR.Items.IndexOf(assignedStudent.FullName);
    if (assignedStudentIndex > -1)
    {
        BRStudents.RemoveAt(assignedStudentIndex);
    }
    BRStudents.Insert(0, assignedStudent);
}
checkedListBoxBR.DataSource = BRStudents;
checkedListBoxBR.DisplayMember = "FullName";
checkedListBoxBR.ValueMember = "StudentID";

…找不到他们。“assignedStudent.FullName”的值不等于其中一项的值；如上所述，“FullName”是CheckedListBox的ValueMember：

一步一步地通过它，学生名单，BRStudents，有2个成员，一个已经被分配的人和另一个人；“指定学生”是指已指定的人员；checkedListBoxBR有三项，即已分配的人员加上另外两项

那么，当被分配的人以全名表示时，为什么被分配的StudentIndex-1是？确实，我没有在这一行中显式指定FullName：

int assignedStudentIndex = 
    checkedListBoxBR.Items.IndexOf(assignedStudent.FullName);

assignedStudent = new Student() {FirstName = assignedStudentFirstname, LastName = assignedStudentLastname, StudentID = ah.StudentID_FK};

…但FullName是类中的计算字段：

public class Student
{
    public int StudentID { get; set; }
    . . .
    public string FirstName { get; set; }
    public string LastName { get; set; }
    . . .
    public string FullName
    {
        get
        {
            return $"{FirstName} {LastName}";
        }
        set { } 
    }
}

那么，为什么“某某”在CheckedListBox的项目中找不到，而它最明显地在那里呢

更新 Olivier的建议似乎不错（“遍历checkedListBoxBR.Items，看看是否在该项的DisplayMember和assignedStudent.FullName之间找到匹配项”）。但是怎么做呢？我想也许像这样的事情可以做到：

for (int i = 0; i < checkedListBoxBR.Items.Count; i++)
{
    if checkedListBoxBR.Items[0].DisplayMember.Equals(assignedStudent.FullName)
    {
        checkedListBoxBR.RemoveAt(i);
    }
}

for（int i=0；i

…但此处不识别“DisplayMember”（也不识别“RemoveAt”）

更新2 回应奥利弗的轻推，我将上面的内容修改为：

for (int i = 0; i < checkedListBoxBR.Items.Count; i++)
{
    if checkedListBoxBR.Items[i].DisplayMember.Equals(assignedStudent.FullName)
    {
        checkedListBoxBR.Items.RemoveAt(i);
    }
}

for（int i=0；i

…但它仍然认为DisplayMember是不受欢迎的属性

更新3 我简化了代码，它运行得很好。以下是简化版本：

// Called whenever the week changes (a new week is navigated to/selected in the combobox)
private void PopulateBibleReadingComboBox()
{
    int BIBLE_READING_TALK_TYPE = 1;
    Student assignedStudent = null;
    List<Student> assignedStudents = null;

    // If the week has been saved, get the student who has been assigned the Bible Reading
    if (currentWeekSaved)
    {
        DateTime currentWeek = Convert.ToDateTime(comboBoxWeekToSchedule.SelectedValue);
        AssignmentHistory ah = AYttFMConstsAndUtils.AssignmentHistList
            .FirstOrDefault(i => i.WeekOfAssignment == currentWeek && i.TalkType == BIBLE_READING_TALK_TYPE);
        if (ah != null)
        {
            var assignedStudentFirstname = AYttFMConstsAndUtils.GetStudentFirstNameForID(ah.StudentID_FK);
            var assignedStudentLastname = AYttFMConstsAndUtils.GetStudentLastNameForID(ah.StudentID_FK);
            assignedStudent = new Student() {FirstName = assignedStudentFirstname, LastName = assignedStudentLastname, StudentID = ah.StudentID_FK};
            // Use the ID to get the student and put him/her in a 1-person list (needed for
            // the subsequent LINQ Union)
            assignedStudents =
                AYttFMConstsAndUtils.StudentsList.Where(i => i.StudentID == ah.StudentID_FK).ToList();
        }
    }
    // Get all the candidates for assignment
    List<Student> BRStudents =
    AYttFMConstsAndUtils.StudentsList.Where(h => h.EnrolledInAYttFM)
        .Where(i => i.RecommendedNextTalkTypeID.Equals(BIBLE_READING_TALK_TYPE))
        .OrderBy(j => j.WeekOfLastAssignment)
        .ToList();
    if (null != assignedStudent) 
    {
        List<Student> allBRStudents = assignedStudents.Union(BRStudents).ToList();
        checkedListBoxBR.DataSource = allBRStudents;
        checkedListBoxBR.DisplayMember = "FullName";
        checkedListBoxBR.ValueMember = "StudentID";
    }
    else // No assigned student found, bind to the candidate students only
    {
        checkedListBoxBR.DataSource = BRStudents;
        checkedListBoxBR.DisplayMember = "FullName";
        checkedListBoxBR.ValueMember = "StudentID";
    }
    // In either case, highlight and check the first one now
    checkedListBoxBR.SelectedIndex = 0;
    checkedListBoxBR.SetItemChecked(0, true);
}

//每周更改时调用（新的一周导航到/在组合框中选择）
private void PopulateBibleReadingComboBox（）
{
int BIBLE_READING_TALK_TYPE=1；
Student assignedStudent=null；
List assignedStudents=null；
//如果本周已被保存，则让被分配阅读圣经的学生阅读
如果（当前周已保存）
{
DateTime currentWeek=Convert.ToDateTime（comboBoxWeekToSchedule.SelectedValue）；
AssignmentHistory ah=AYTTFMConstandUtils.AssignmentHistList
.FirstOrDefault（i=>i.WeekOfAssignment==currentWeek&&i.TalkType==BIBLE\u READING\u TALK\u TYPE）；
如果（啊！=null）
{
var assignedStudentFirstname=AYttFMConstsAndUtils.GetStudentFirstNameForID（ah.StudentID_FK）；
var assignedStudentLastname=AYttFMConstsAndUtils.GetStudentLastNameForID（ah.StudentID_FK）；
assignedStudent=new Student（）{FirstName=assignedStudentFirstname，LastName=assignedStudentLastname，StudentID=ah.StudentID_FK}；
//使用ID获取该学生，并将他/她放入一人名单中（需要
//随后的LINQ联盟）
指定学生=
AyttfmConstandUtils.StudentsList.Where（i=>i.StudentID==ah.StudentID_FK）.ToList（）；
}
}
//把所有的候选人都派出去
列出学生名单=
AyttfmConstandUtils.StudentsList.Where（h=>h.EnrolledAyttfm）
其中（i=>i.RecommendedNextTalkTypeID.Equals（圣经\阅读\谈话\类型））
.OrderBy（j=>j.weekofrastassignment）
.ToList（）；
如果（null！=已分配的学生）
{
列出所有BRStudents=assignedStudents.Union（BRStudents.ToList（）；
checkedListBoxBR.DataSource=所有BRStudents；
checkedListBoxBR.DisplayMember=“FullName”；
checkedListBoxBR.ValueMember=“StudentID”；
}
else//未找到指定学生，仅绑定到候选学生
{
checkedListBoxBR.DataSource=BRStudents；
checkedListBoxBR.DisplayMember=“FullName”；
checkedListBoxBR.ValueMember=“StudentID”；
}
//无论哪种情况，现在都突出显示并检查第一个
checkedListBoxBR.SelectedIndex=0；
checkedListBoxBR.SetItemChecked（0，true）；
}

我发现有两件事不对

首先，在检查某个项目是否存在后，填充

checkedListBoxBR

第二，你在比较苹果和桔子

checkedListBoxBR.Items

是对象的集合，您可以通过indexOf将其与字符串（

assignedStudent.FullName

）进行比较。那是行不通的

更好的解决方案是遍历

checkedListBoxBR.Items

，查看是否在项目的

DisplayMember

和

assignedStudent.FullName

之间找到匹配项

---

或者您可以在indexOf调用中使用Student对象，但是您需要确保实现IEquatable、override Equals、GetHashCode等。

您的

checkedListBoxBR

的项属于

Student

类型，因为您的数据源中的项属于

Student

类型：

List<Student> BRStudents = [...]
checkedListBoxBR.DataSource = BRStudents;

此外，您可能希望

编辑： 正如@olivier de meulder正确指出的，您需要将这些行移到查找上方，以使任何选项正常工作：

checkedListBoxBR.DataSource = BRStudents;
checkedListBoxBR.DisplayMember = "FullName";
checkedListBoxBR.ValueMember = "StudentID";

---

这可能是因为IndexOf在将对象绑定到BRStudents时需要一个对象。在循环中：“checkedListBoxBR.Items[i]”。索引i而不是0。并将removeAt应用于checkedListBoxBR.Items。我没有广泛使用Windows窗体，但请尝试

checkedListBoxBR.Items[I]。ToString（）==assignedStudent.FullName

DisplayMember不是student的属性。强制转换为学生并使用全名。您需要在

之前的表达式周围添加括号。全名

checkedListBoxBR.DataSource = BRStudents;
checkedListBoxBR.DisplayMember = "FullName";
checkedListBoxBR.ValueMember = "StudentID";