VB.Net程序设计:IComparer的应用，按两个不同类的某个属性比较排序

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比较方法：两个不同的类，其中有一个属性是相同类型的，如日期，或者字符。

自定义IComparer，实现比较方法。

Imports System.RuntimeImports System.CollectionsPublic Class Form1    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click        Dim ArList As New ArrayList        With ArList            .Add(New Duty(Date.Now, "now"))            .Add(New DutyTemp(Date.Today, "today"))            .Add(New Duty(Date.Today.AddHours(1), "today+1h"))            .Add(New DutyTemp(Date.Today.AddDays(1), "today-1day"))            .Add(New Duty(Date.Today.AddHours(-1), "today-1h"))            .Add(New Duty(Date.Today.AddDays(5), "today-5day"))            .Add(New DutyTemp(Date.Today.AddDays(-8), "today-8day"))        End With        ArList.Sort(New DutyComparer)        For Each obj As Object In ArList            Debug.Print(obj.ToString)        Next    End SubEnd ClassPublic Class DutyComparer    Implements IComparer    Public Function Compare(x As Object, y As Object) As Integer Implements System.Collections.IComparer.Compare        Dim dtm1, dtm2 As Date        Select Case x.GetType            Case GetType(Duty)                dtm1 = CType(x, Duty).DateFrom            Case GetType(DutyTemp)                dtm1 = CType(x, DutyTemp).TimeFrom        End Select        Select Case y.GetType            Case GetType(Duty)                dtm2 = CType(y, Duty).DateFrom            Case GetType(DutyTemp)                dtm2 = CType(y, DutyTemp).TimeFrom        End Select        Return Date.Compare(dtm1, dtm2)    End FunctionEnd Class'--如果兩個不同類可以抽象處理，實現相同接口，就比較容易點。Public Class Duty    Property DateFrom As Date    Property DutyName As String    Sub New(dtmFrom As Date, strName As String)        DateFrom = dtmFrom        DutyName = strName    End Sub    Public Overrides Function ToString() As String        Return String.Format("{0}-{1}", DateFrom.ToString, DutyName)    End FunctionEnd ClassPublic Class DutyTemp    Property TimeFrom As Date    Property DutyTempName As String    Sub New(dtmFrom As Date, strName As String)        TimeFrom = dtmFrom        DutyTempName = strName    End Sub    Public Overrides Function ToString() As String        Return String.Format("{0}-{1}", TimeFrom.ToString, DutyTempName)    End FunctionEnd Class

对比结果：

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