Deep Equality Compare of Nested Dictionaries and Lists

CollectionEquality.vb

Imports System.Collections.Generic 

Namespace AUL 
  Partial Class Utils 

    Private Shared _valueComparer As EqualityComparer(Of Object) = EqualityComparer(Of Object).Default 

    ''' <summary> 
    ''' 
    ''' There is no pre-given implementation of .Equals 
    ''' that deeply compares based on value instead of 
    ''' reference. The standard .Equals only returns 
    ''' true if the two Dictionaries are the same object 
    ''' 
    ''' </summary> 
    ''' <param name="a"></param> 
    ''' <param name="b"></param> 
    ''' <returns></returns> 
    ''' <remarks></remarks> 
    Public Shared Function CollectionsAreEqual( _ 
        ByVal a As Object, _ 
        ByVal b As Object) As Boolean 

      Dim result As Boolean = True 

      If (a.Equals(b)) Then Return True 
      If (a Is Nothing Or b Is Nothing) Then Return True 
      If (Not a.Count.Equals(b.Count)) Then Return False 
      If (Not a.GetType.Equals(b.GetType)) Then Return False

      ' we can assume both types are the same due to the type check above 
      ' call the corresponding helper method based on whether this is 
      ' a dictionary or a list 
      If (a.GetType.Equals(GetType(Dictionary(Of String, Object)))) Then 
        result = result AndAlso CollectionDictionariesAreEqualHelper(a, b) 
      ElseIf (a.GetType.Equals(GetType(List(Of Object)))) Then 
        result = result AndAlso CollectionListsAreEqualHelper(a, b) 
      Else 
        ' Nothing to iterate over, we should have returned before getting here 
      End If 

      Return result 

    End Function 

    Private Shared Function CollectionDictionariesAreEqualHelper(ByVal a As Dictionary(Of String, Object), _ 
                                                                 ByVal b As Dictionary(Of String, Object)) As Boolean 
      Dim result As Boolean = True 

      For Each kvp As KeyValuePair(Of String, Object) In a 
        Dim valueA As Object = kvp.Value 
        Dim valueB As Object 

        ' if the second dictionary has the key 
        If (Not b.TryGetValue(kvp.Key, valueB)) Then Return False 

        ' We don't care what a and b are, but the CollectionsAreEqual 
        ' Function should take care of every case of object 
        result = (result And CollectionsAreEqual(valueA, valueB)) 

        ' Terminate if this loop caused an inequality 
        If (Not result) Then Return False 
      Next 

      Return result 
    End Function 

    Private Shared Function CollectionListsAreEqualHelper(ByVal a As List(Of Object), _ 
                                                          ByVal b As List(Of Object)) As Boolean 
      Dim result As Boolean = True 

      Dim i As Integer 
      For i = 0 To a.Count - 1 

        Dim valueA As Object = a(i) 
        Dim valueB As Object = b(i) 

        ' We don't care what a and b are, but the CollectionsAreEqual 
        ' Function should take care of every case of object 
        result = (result And CollectionsAreEqual(valueA, valueB)) 
        If (Not result) Then Return False 
      Next 

      Return result 
    End Function 


  End Class 
End Namespace 

CollectionEqualityTest.vb

Imports System.Text 
Imports Microsoft.VisualStudio.TestTools.UnitTesting 
Imports System.Collections.Generic 

<TestClass()> Public Class CollectionEqualityTest

  <TestMethod()> Public Sub EmptyCollections() 
    Dim h1 As New Dictionary(Of String, Object) 
    Dim h2 As New Dictionary(Of String, Object) 
    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 
  End Sub 

  <TestMethod> Public Sub SmallSameCollections() 
    Dim h1 As New Dictionary(Of String, Object) 
    Dim h2 As New Dictionary(Of String, Object) 

    h1.Add("1", "2") 
    h2.Add("1", "2") 


    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 
  End Sub 

  <TestMethod> Public Sub MultipleEntries() 
    Dim h1 As New Dictionary(Of String, Object) 
    Dim h2 As New Dictionary(Of String, Object) 

    h1.Add("1", "2") 
    h2.Add("1", "2") 
    h1.Add("one", "two") 
    h2.Add("one", "two") 
    h1.Add("and 1", "and 2") 
    h2.Add("and 1", "and 2") 
    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 

  End Sub 

  <TestMethod> Public Sub NestedHashes() 
    Dim h1 As New Dictionary(Of String, Object) 
    Dim h2 As New Dictionary(Of String, Object) 

    Dim h3 As New Dictionary(Of String, Object) 
    Dim h4 As New Dictionary(Of String, Object) 

    h1.Add("1", "2") 
    h2.Add("1", "2") 
    h1.Add("one", h3) 
    h2.Add("one", h4) 
    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 
  End Sub 

  <TestMethod> Public Sub Lists() 
    Dim h1 As New List(Of Object) 
    Dim h2 As New List(Of Object) 

    h1.Add(1) 
    h1.Add(2) 
    h2.Add(1) 
    h2.Add(2) 

    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 
  End Sub 

  <TestMethod> Public Sub HashesWithLists() 
    Dim h1 As New Dictionary(Of String, Object) 
    Dim h2 As New Dictionary(Of String, Object) 

    Dim h3 As New List(Of Object) 
    Dim h4 As New List(Of Object) 

    h3.Add(1) 
    h3.Add(2) 
    h4.Add(1) 
    h4.Add(2) 

    h1.Add("1", "2") 
    h2.Add("1", "2") 
    h1.Add("one", h3) 
    h2.Add("one", h4) 
    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 

  End Sub 

  <TestMethod> Public Sub DeeplyNestedData() 
    Dim h1 As Dictionary(Of String, Object) = TestData.GenerateGroupData 
    Dim h2 As Dictionary(Of String, Object) = TestData.GenerateGroupData 

    Assert.IsTrue(AUL.Utils.CollectionsAreEqual(h1, h2)) 
  End Sub 


End Class