要求业务验证的情况大致可以分为3类

1、某一个值本身需要验证

2、仅当另外一个值出现时，某一个值需要验证

3、仅当另外一个数据集里面包含的某一个数据满足某个条件时，某一个值需要验证

业务逻辑的验证要求验证方法集中处理，尽量避免在整个系统中对同一个值存在多个业务验证。

验证：返回true或false的方法，该方法必须包含两个参数，1、验证数据本身；2、验证数据的处理方法

验证中必须理解的技术：

delegate：表示委托，委托是一种数据结构，它引用静态方法或引用类实例及该类的实例方法。要求被引用方法的参数和返回值和delegate声明的方法一致的类。该类的方法就可以被delegate类型调用。

一下为两个例子：

例子一：

Public Class SamplesDelegate

   ' 为一个方法申明委托  
   Delegate Function myMethodDelegate(myInt As Integer) As [String]

   ' 申明委托能够指向的方法
   Public Class mySampleClass

      ' 定义需要实例化的方法.
      Public Function myStringMethod(myInt As Integer) As [String]
         If myInt > 0 Then
            Return "positive"
         End If
         If myInt < 0 Then
            Return "negative"
         End If
         Return "zero"
      End Function 'myStringMethod

      ' 定义静态方法
      Public Shared Function mySignMethod(myInt As Integer) As [String]
         If myInt > 0 Then
            Return "+"
         End If
         If myInt < 0 Then
            Return "-"
         End If
         Return ""
      End Function 'mySignMethod
   End Class 'mySampleClass

   Public Shared Sub Main()

      ' 为每个方法申明一个委托myD1,myD2.
      Dim mySC As New mySampleClass()
      Dim myD1 As New myMethodDelegate(AddressOf mySC.myStringMethod)'引用实例方法
      Dim myD2 As New myMethodDelegate(AddressOf mySampleClass.mySignMethod)'引用静态方法

      ' 通过委托调用.
      Console.WriteLine("{0} is {1}; use the sign ""{2}"".", 5, myD1(5), myD2(5))
      Console.WriteLine("{0} is {1}; use the sign ""{2}"".", - 3, myD1(- 3), myD2(- 3))
      Console.WriteLine("{0} is {1}; use the sign ""{2}"".", 0, myD1(0), myD2(0))

   End Sub 'Main

End Class 'SamplesDelegate

例子二：

Public Class SortClass

   '声明委托
   Delegate Function Compare(ByVal x As Integer, _
                                 ByVal y As Integer) As Boolean

   '申明委托指向的实例方法
   Function CompareValues(ByVal X As Integer, _
                          ByVal Y As Integer) As Boolean
      If X > Y Then
         CompareValues = True
      Else
         CompareValues = False
      End If
   End Function

   '声明使用委托的方法
   Sub SelectionSort(ByVal IsGreaterThan As Compare, _
                     ByVal IntArray() As Integer)
      Dim MaxVal As Integer
      Dim MaxIndex As Integer
      Dim i, j As Integer

      ' Step through the elements in the array starting with the
      ' last element in the array.
      For i = UBound(IntArray) To 1 Step -1
         MaxVal = IntArray(i)
         MaxIndex = i
         For j = 1 To i
            ' 使用委托.
            If IsGreaterThan.Invoke(IntArray(j), MaxVal) Then
               MaxVal = IntArray(j)
               MaxIndex = j
            End If
         Next j
         ' 使用委托.
         If IsGreaterThan.Invoke(i, MaxIndex) Then
            IntArray(MaxIndex) = IntArray(i)
            IntArray(i) = MaxVal
         End If
      Next i
   End Sub
End Class

Class Class1
   Sub SortArray()
      '声明被委托指向的实例化对象
      Dim Sort As New SortClass()
      Dim arr1() As Integer = {1, 5, 3, 2, 7, 22, 5, 54, 12}
      Sort.SelectionSort(AddressOf Sort.CompareValues, arr1)
      MsgBox("Array sorted.")
   End Sub
End Class

   '测试 
   Private Sub Button1_Click(ByVal sender As System.Object, _
                             ByVal e As System.EventArgs) _
                             Handles Button1.Click
      Dim c As New Class1()
      c.SortArray()
   End Sub