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我成功地将显示/值对添加到这样的组合框中:

List<Student> BRStudents =
        studentsList.Where(h => h.EnrolledInAYttFM)
            .Where(i =>     
    i.RecommendedNextTalkTypeID.Equals(BIBLE_READING_TALK_TYPE))
            .OrderBy(j => j.WeekOfLastAssignment)
            .ToList();
    comboBoxBR.DataSource = BRStudents;
    comboBoxBR.DisplayMember = "FullName";
    comboBoxBR.ValueMember = "StudentID";

...但我随后(在某些情况下)想向 comboBoxBR 添加另一个项目,该项目不在 BRStudents 列表中。如果我尝试这样做:

AssignmentHistory ah = AYttFMConstsAndUtils.AssignmentHistList
    .FirstOrDefault(i => i.WeekOfAssignment == currentWeek && i.TalkType == 1);
string fullName = AYttFMConstsAndUtils.GetStudentFullNameForID(ah.StudentID_FK);
comboBoxBR.Items.Add(fullName);

...我得到,“设置 DataSource 属性时无法修改项目集合。”

真的,我想做这样的事情:

comboBoxBR.Items.Add(fullName, ah.StudentID_FK);

有没有办法将两个结果(Student 列表和单个 AssignmentHistory)组合到 Dictionary 或一些这样的集合中,然后将分配为 comboBoxBR 的 DataSource?

为了全面披露,以下是 Student 和 AssignmentHistory 的定义:

public class Student
{
    public int StudentID { get; set; }
    public int FamilyID { get; set; }
    public bool EnrolledInAYttFM { get; set; }
    public DateTime DateEnrolledOrHiatusAYttFM { get; set; }
    public bool GivesBibleReading { get; set; }
    public bool PresentsICRVBS { get; set; }
    public bool IsHouseholder { get; set; }
    public bool IsMale { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string EmailAddr { get; set; }
    public DateTime WeekOfLastAssignment { get; set; }
    public int RecommendedNextTalkTypeID { get; set; }
    public int NextCounselPoint { get; set; }
    public string FullName => $"{FirstName} {LastName}";
}

public class AssignmentHistory
{
    public DateTime WeekOfAssignment { get; set; }
    public int TalkType { get; set; } 
    public int StudentID_FK { get; set; }
    public int AssistantID_FK { get; set; } 
    public int CounselPoint { get; set; }
    public bool HasBeenEmailed { get; set; }
    public bool SlipHasBeenPrinted { get; set; }        
}
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1 回答 1

1

而不是将元素添加到组合的 Items 集合(如果您设置了 DataSource,则不可能)首先想到的是向List<Students>用作 DataSource 的自身添加元素,但这并没有达到您的目标,因为没有用于通知 ComboBox DataSource 有一个新元素的机制。除非您将列表重新绑定到组合框,否则您看不到添加的元素。为此,您首先需要取消绑定先前的 DataSource,然后再次重新绑定列表。

// Assuming a lot about your student class, hope it's clear the intention
BRStudents.Add(new Student() { newName = "ANewStudent", ID = 1} );
comboBoxBR.DataSource = null;
comboBoxBR.DataSource = BRStudents;
comboBoxBR.DisplayMember = "FullName";
comboBoxBR.ValueMember = "StudentID";

但是,有一个更好的解决方案,它是类BindingList(T)
此类能够刷新绑定它的实例的对象。

因此,当您第一次绑定组合时,您必须编写

BindingList<Student> bl = new BindingList<Student>(BRStudents);
comboBoxBR.DataSource = bl;
comboBoxBR.DisplayMember = "FullName";
comboBoxBR.ValueMember = "StudentID";

以及当您想向您编写的列表中添加新元素时
(如果需要,请在全局范围内移动 bl)

bl.Add(new Student() { newName = "ANewStudent", ID = 1} );

该文档指出您应该调用 ResetBindings 来强制刷新控件,但这似乎并不总是需要......

于 2016-02-21T17:00:51.163 回答