如何将 DisplayMember 和 ValueMember 添加到具有指定数据源的单个 ComboBox 项？

Question

我成功地将 Display/Value 对添加到组合框，如下所示：

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，该项目不存在于 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);

...我明白了，"Items collection cannot be modified when the DataSource property is set."

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）组合成字典或类似的集合，然后将 that 指定为数据源组合框BR?

为了完整披露，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; }        
}

Answer 1

首先想到的不是将元素添加到组合的 Items 集合（如果设置了数据源，则不可能），而是将元素添加到用作数据源的 List<Students> 本身，但这没有到达您的 objective 因为没有适当的机制来通知 ComboBox DataSource 有一个新元素。除非将列表重新绑定到组合框，否则看不到添加的元素。为此，您首先需要取消绑定以前的数据源，然后重新绑定列表。

// 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，那就是 class BindingList(T)
此 class 能够刷新您绑定其实例的对象。

所以第一次绑定combo的时候要写

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，在全局范围内移动 bl）

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

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

如何将 DisplayMember 和 ValueMember 添加到具有指定数据源的单个 ComboBox 项？

How can I add a DisplayMember and ValueMember to a single ComboBox Item that has an assigned DataSource?

c#

linq

combobox

generic-list

valuemember