Question

获取表单代码：

Imports TechSupportData

Public Class frmOpenIncidents

Private Sub frmOpenIncidents_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Dim incidentList As List(Of Incident)
    Try
        incidentList = IncidentDB.GetIncidents
        If incidentList.Count > 0 Then
            Dim incident As Incident
            For i As Integer = 0 To incidentList.Count - 1
                incident = incidentList(i)
                lvIncidents.Items.Add(incident.ProductCode)
                lvIncidents.Items(i).SubItems.Add(incident.DateOpened)
                lvIncidents.Items(i).SubItems.Add(incident.CustomerID)
                lvIncidents.Items(i).SubItems.Add(incident.TechID)
                lvIncidents.Items(i).SubItems.Add(incident.Title)
            Next
        Else
            MessageBox.Show("All Incidents are taken care of")
            Me.Close()
        End If
    Catch ex As Exception
        MessageBox.Show(ex.Message, ex.GetType.ToString)
        Me.Close()
    End Try
End Sub
End Class

继续与之合作的班级：

Imports System.Data.SqlClient

Public Class IncidentDB
    Public Shared Function GetIncidents() As List(Of IncidentDB)
        Dim incidentList As New List(Of IncidentDB)
        Dim connection As SqlConnection = TechSupportDB.GetConnection
        Dim selectStatement As String _
            = "SELECT CustomerID, ProductCode, TechID, DateOpened, Title" _
            & "FROM(Incidents)" _
            & "WHERE DateClosed IS NULL"
        Dim selectCommand As New SqlCommand(selectStatement, connection)
        Try
            connection.Open()
            Dim reader As SqlDataReader = selectCommand.ExecuteReader()
            Dim incident As Incident
            Do While reader.Read
                incident = New Incident
                incident.IncidentID = reader("IncidentID").ToString
                incident.CustomerID = reader("CustomerID").ToString
                incident.ProductCode = reader("ProductCode").ToString
                incident.DateOpened = reader("DateOpened").ToString
            Loop
            reader.Close()
        Catch ex As Exception
            Throw ex
        Finally
            connection.Close()
        End Try
        Return incidentList
    End Function
End Class

这是我从Visual Studio得到的错误：

错误1类型'System.Collections.Generic.List（Of TechSupportData.IncidentDB）'的值无法转换为'System.Collections.Generic.List（Of TechSupportData.Incident）'。 C：\ Users \ Cody \ Desktop \ School \ Current \ ITECH4269 Visual Basic \ Assignment2CodyStewart \ Assignment2CodySteawrt \ Assignment2CodySteawrt \ frmOpenIncidents.vb 8 28 Assignment2CodySteawrt

非常感谢任何指导或建议，非常感谢。

Answer 1

在课程frmOpenIncidents中，您已将incidentList定义为突发事件列表：

Dim incidentList As List(Of Incident)

然后设置它：

incidentList = IncidentDB.GetIncidents

但是，IncidentDB方法被定义为返回Incident * DB *列表：

Public Shared Function GetIncidents() As List(Of IncidentDB)

解决方案可能是将第一个定义更改为此？

Dim incidentList As List(Of IncidentDB)

您需要为类选择一个名称 - Incident或IncidentDB - 并始终使用它来消除所有类似的错误。

为什么这个VB代码失败了？

1 个答案: