ComboBox不显示DisplayMember [英] ComboBox not showing DisplayMember

问题描述

我想在组合框中显示问题ID，以便在文本框中重现匹配的问题。然而，不是问题ID出现，我接收这个所有5问题ID：

WCInterface.ucQuestions + QuestionWCInterface.ucQuestions + / p>

我的代码：

  Private loaded As Boolean = False 
 
 Private Sub ucQuestions_Load（ByVal sender As System.Object，ByVal e As System.EventArgs）句柄MyBase.Load 
 
 cmbQuestion.DisplayMember =Question_ID
 cmbQuestion.ValueMember =Question_ID
 cmbQuestion.DataSource = retrieveQuestions（）'当窗体加载
 
 loaded = True 
 
 End Sub 
 
 Private Sub cmbQuestion_SelectedIndexChanged（ByVal sender As System.Object，ByVal e As System.EventArgs）句柄cmbQuestion.SelectedIndexChanged 
如果（loaded）then 
 
 cmbQuestion.DisplayMember =Question_ID
 cmbQuestion.ValueMember =Question_ID
 cmbQuestion.DataSource = Nothing'当表单加载时重置数据源
 cmbQuestion.DataSource = retrieveQuestions b End If 
 End Sub 
 
公共函数retrieveQuestions（）作为列表（问题）
 
 Dim typeList作为新列表（问题）
 Dim Str as String =SELECT Question_ID，Question_Text FROM Question
 Try 
使用conn作为新的SqlClient.SqlConnection（DBConnection）
 conn.Open（）
使用cmdQuery As New SqlClient。使用drResult As SqlClient.SqlDataReader = cmdQuery.ExecuteReader（）
虽然drResult.Read 
 typeList.Add（新问题（drResult（Question_ID），drResult Question_Text）））
 End While 
结束使用'自动关闭连接
结束使用
结束使用
 
 Catch ex As Exception 
 
 MsgBox（问题列表例外：& ex.Message& vbNewLine& Str）
 
结束尝试
 
返回typeList 
 
结束函数
  

对于我如何显示问题ID，谢谢任何建议。

解决方案

p>您没有发布您的Question类，但DisplayMember和ValueMember字段不匹配Question类中的属性字段：

它应该看起来像这样：

 公共类问题
 Property QuestionID As Integer 
 Property QuestionText As String 
 
 Public Sub New（q_ID As Integer，q_Text As String）
 QuestionID = q_ID 
 QuestionText = q_Text 
 End Sub 
结束类
  
 
 
 
然后，您的数据源属性将如下所示：
  cmbQuestion.DisplayMember =QuestionID
 cmbQuestion.ValueMember =QuestionID
 cmbQuestion.DataSource = retrieveQuestions（）
  
 
I'm trying to display the Question ID's in the combo box, in order to reproduce the matching question in a text box. However rather than the Question ID's appearing, I am receiving this for all 5 question ID's: 

  
WCInterface.ucQuestions+QuestionWCInterface.ucQuestions+Question
My code: 
Private loaded As Boolean = False

Private Sub ucQuestions_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    cmbQuestion.DisplayMember = "Question_ID"
    cmbQuestion.ValueMember = "Question_ID"
    cmbQuestion.DataSource = retrieveQuestions() 'when form loads

    loaded = True

End Sub

Private Sub cmbQuestion_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbQuestion.SelectedIndexChanged
    If (loaded) Then

        cmbQuestion.DisplayMember = "Question_ID"
        cmbQuestion.ValueMember = "Question_ID"
        cmbQuestion.DataSource = Nothing 'Resets data source
        cmbQuestion.DataSource = retrieveQuestions() 'when form loads
    End If
End Sub

Public Function retrieveQuestions() As List(Of Question)

    Dim typeList As New List(Of Question)
    Dim Str As String = "SELECT Question_ID, Question_Text FROM Question"
    Try
        Using conn As New SqlClient.SqlConnection(DBConnection)
            conn.Open()
            Using cmdQuery As New SqlClient.SqlCommand(Str, conn)
                Using drResult As SqlClient.SqlDataReader = cmdQuery.ExecuteReader()
                    While drResult.Read
                        typeList.Add(New Question(drResult("Question_ID"), drResult("Question_Text")))
                    End While
                End Using 'Automatically closes connection
            End Using
        End Using

    Catch ex As Exception

        MsgBox("Question List Exception: " & ex.Message & vbNewLine & Str)

    End Try

    Return typeList

End Function
I'd appreciate any suggestions as to how I display the Question ID's, thankyou
解决方案
You didn't post your Question class, but the DisplayMember and ValueMember fields aren't matching the property fields in the Question class:

It should look something like this:
Public Class Question
  Property QuestionID As Integer
  Property QuestionText As String

  Public Sub New(q_ID As Integer, q_Text As String)
    QuestionID = q_ID
    QuestionText = q_Text
  End Sub
End Class
Then your data source properties would look like this:
cmbQuestion.DisplayMember = "QuestionID"
cmbQuestion.ValueMember = "QuestionID"
cmbQuestion.DataSource = retrieveQuestions() 


                        
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