'
'ListViewSortComparer was made by William Wood 2005.
'
'''
''' Allows you to sort all the items in a ListView control by different columns, orders and datatypes.
'''
'''
'''
''' This example shows you how to sort a collection of items in the second column of a ListView control
''' containing numbers in descending order.
'''
''' ListView1.ListViewItemSorter = New ListViewSortComparer(1, SortOrder.Descending, ListViewSortComparer.SourceDataType.Numerical)
''' ListView1.Sort()
'''
'''
'''
Public Class ListViewSortComparer
Implements System.Collections.IComparer
'''
''' Indicates the column index to be sorted.
'''
Private _ColumnIndex As Integer
'''
''' Holds the order in which the data is to be sorted.
'''
Private _SortOrder As SortOrder = SortOrder.Ascending
'''
''' Holds the type of data in the column so the appropiate comparer can be used
'''
Private _DataType As SourceDataType = SourceDataType.Text
#Region " Overloaded Public Sub New "
'''
''' Creates a new instance of the comparer, the order used to sort the ListViewItems in the first column.
'''
''' The SortOrder type specifying the order in which the data in columnIndex
''' should be sorted.
'''
''' Performs a text based comparison of the items in the first column of the ListView control that uses this comparer using the sort order specified
''' by sort.
'''
Public Sub New(ByVal sort As SortOrder)
_ColumnIndex = 0
_SortOrder = sort
End Sub
'''
''' Creates a new instance of the comparer, specifying the column to sort by and the order used to sort the ListViewItems.
'''
''' The zero-based index specifying the column to sort.
''' The SortOrder type specifying the order in which the data in columnIndex
''' should be sorted.
'''
''' Performs a text based comparison of the items in the ListView control that uses this comparer using the options specified
''' by the arguments above.
'''
Public Sub New(ByVal columnIndex As Integer, ByVal sort As SortOrder)
_ColumnIndex = columnIndex
_SortOrder = sort
End Sub
'''
''' Creates a new instance of the comparer, specifying the column to sort by and the order used to sort the ListViewItems and the
''' datatype of the elements in the column.
'''
''' The zero-based index specifying the column to sort.
''' The SortOrder type specifying the order in which the data in columnIndex
''' should be sorted.
''' The datatype of the items in the column specified by columnIndex.
'''
''' Performs a comparision of all the items in the ListView control using the datatype specified by the dataType
''' argument. You must ensure you select the correct datatype for all the items, otherwise you may receive unexpected results.
''' For Example, if you sort a collection of numbers as text, it will sort them as 1,10,11,2,22,25,7,8 instead of 1,2,7,8,10,11,22,25.
'''
Public Sub New(ByVal columnIndex As Integer, ByVal sort As SortOrder, ByVal dataType As SourceDataType)
_ColumnIndex = columnIndex
_SortOrder = sort
_DataType = dataType
End Sub
#End Region
'''
''' Compares two ListViewItems using a datatype comparison specified by SourceDataType.
'''
''' The first item to compare.
''' The second item to compare.
''' A value indicating the positions of the two passed objects relative to each other.
'''
'''
''' Return Value
''' Meaning
'''
''' - Less than zeroobject1 is less than object2.
''' - Zeroobject1 is equal to object2.
''' - Greater than zeroobject1 is greater than object2.
'''
'''
'''
''' Compares all the items in the ListView control to allow them to be sorted.
''' This function uses the parameters set in the class's constructor to specify its properties such as the sort order and the datatype comparison to be used.
''' This function will also automatically move null items to the top of the collection when performing an ascending sort, or move them to the bottom of the collection
''' when performing a descending sort.
'''
''' This exception is thrown when the DataType is invalid for the type of data present in the column.
''' For example, sorting a collection of names as SourceDataType.DateTime.
Public Function Compare(ByVal object1 As Object, ByVal object2 As Object) As Integer Implements System.Collections.IComparer.Compare
'
'Holds the two items to be compared, converting them both to ListViewItems
Dim ListViewItem1 As ListViewItem = CType(object1, ListViewItem)
Dim ListViewItem2 As ListViewItem = CType(object2, ListViewItem)
'
'Initial null checking to ensure that there is valid data in the item being compared
'to reduce the chance of exceptions being raised due to no objects being referenced
If CheckNulls(ListViewItem1, ListViewItem2) <> 0 Then 'Checks to see if CheckNulls doesn't return 0 i.e. there is a null SubItem present
Return CheckNulls(ListViewItem1, ListViewItem2) 'It returned 0. Returns the position returned by CheckNulls that indicates where the null item should be moved to
End If
If _SortOrder = SortOrder.Ascending Then 'Checks to see if it should sort in Ascending order
'It should sort in ascending order
If _DataType = SourceDataType.Text Then 'Checks to see if it should sort the items as text
'It should sort the items as text
Return String.Compare(ListViewItem1.SubItems(_ColumnIndex).Text, ListViewItem2.SubItems(_ColumnIndex).Text)
ElseIf _DataType = SourceDataType.Numerical Then 'Checks to see if it should sort the items as integers
'It should sort the items as Integers
Return Integer.Parse(ListViewItem1.SubItems(_ColumnIndex).Text) - Integer.Parse(ListViewItem2.SubItems(_ColumnIndex).Text)
ElseIf _DataType = SourceDataType.DateTime Then 'Checks to see if it should sort the items as date/time
'It should sort the items as date/time
Return Date.Compare(Date.Parse(ListViewItem1.SubItems(_ColumnIndex).Text), Date.Parse(ListViewItem2.SubItems(_ColumnIndex).Text))
ElseIf _DataType = SourceDataType.Percentage Then 'Checks to see if it should sort the items as percentages
'It should sort the items as percentages
'Return Single.Parse(CleanPercentage(ListViewItem1.SubItems(_ColumnIndex).Text)) - Single.Parse(CleanPercentage(ListViewItem2.SubItems(_ColumnIndex).Text))
Return SingleComparer(Single.Parse(CleanPercentage(ListViewItem1.SubItems(_ColumnIndex).Text)), Single.Parse(CleanPercentage(ListViewItem2.SubItems(_ColumnIndex).Text)))
ElseIf _DataType = SourceDataType.Single Then 'Checks to see if it should sort the items as singles
'It should sort the items as singles
'Return Single.Parse(ListViewItem1.SubItems(_ColumnIndex).Text) - Single.Parse(ListViewItem2.SubItems(_ColumnIndex).Text)
Return SingleComparer(Single.Parse(ListViewItem1.SubItems(_ColumnIndex).Text), Single.Parse(ListViewItem2.SubItems(_ColumnIndex).Text))
End If
ElseIf _SortOrder = SortOrder.Descending Then 'Checks to see if it should sort in Descending order
'It should sort in descending order
If _DataType = SourceDataType.Text Then 'Checks to see if it should sort the items as text
'It should sort the items as text
Return String.Compare(ListViewItem2.SubItems(_ColumnIndex).Text, ListViewItem1.SubItems(_ColumnIndex).Text)
ElseIf _DataType = SourceDataType.Numerical Then 'Checks to see if it should sort the items as integers
'It should sort the items as Integers
Return Integer.Parse(ListViewItem2.SubItems(_ColumnIndex).Text) - Integer.Parse(ListViewItem1.SubItems(_ColumnIndex).Text)
ElseIf _DataType = SourceDataType.DateTime Then 'Checks to see if it should sort the items as date/time
'It should sort the items as date/time
Return Date.Compare(Date.Parse(ListViewItem2.SubItems(_ColumnIndex).Text), Date.Parse(ListViewItem1.SubItems(_ColumnIndex).Text))
ElseIf _DataType = SourceDataType.Percentage Then 'Checks to see if it should sort the items as percentages
'It should sort the items as percentages
Return SingleComparer(Single.Parse(CleanPercentage(ListViewItem2.SubItems(_ColumnIndex).Text)), Single.Parse(CleanPercentage(ListViewItem1.SubItems(_ColumnIndex).Text)))
ElseIf _DataType = SourceDataType.Single Then 'Checks to see if it should sort the items as singles
'It should sort the items as singles
Return SingleComparer(Single.Parse(ListViewItem2.SubItems(_ColumnIndex).Text), Single.Parse(ListViewItem1.SubItems(_ColumnIndex).Text))
End If
End If
Return 0 'Returns 0 because no valid comparison could be made
End Function
'''
''' Checks the passed ListViewItems to see if they contain valid data for comparisons.
'''
''' The first ListViewItem that will be used in a comparison.
''' The second ListViewItem that will be used in a comparison.
''' A value indicating whether it is valid or not.
''' This function checks the values of listViewItem1 and
''' listViewItem2 to ensure that they contain valid data for comparisons to be made.
''' It does this by first checking that the column index passed to the comparer to compare on is a valid item in each of the ListViewItems
''' (i.e. it exists in their SubItems collections). It will then check to see if it actually contains any data
''' for a comparison to be made.
''' If the two checks checkout for both of the arguments, then the function will return a value of 0 which indicates that the arguments contain
''' valid data for a comparison to be made.
''' However, if either of the two checks fail for either of the arguments, then the function will return a valid of either -1 or 1 which
''' indicates the position of listViewItem1 in comparision to listViewItem2
''' which can then be used by the calling subroutine to use as it's return value if it's a comparer.
''' Please note, this function does not compare the value of items, this needs to be done after the checking performed by this function. This
''' function mearly checks for invalid data that may cause a comparer to raise an exception if a null item is encounted so they can be automatically
''' moved to the top or bottom depending on the sort performed.
Private Function CheckNulls(ByVal listViewItem1 As ListViewItem, ByVal listViewItem2 As ListViewItem) As Integer
If _SortOrder = SortOrder.Ascending Then 'Checks to see if it should perform an ascending sort
'
'It should sort in ascending order
If listViewItem1.SubItems.Count <= _ColumnIndex Then 'Checks to see if the number of items in ListViewItem1 is <= the column index supplied i.e. no subitem exists at that position
Return -1 'The number of SubItems is <= _ColumnIndex. Returns -1 indicating that it should be moved up
End If
If listViewItem2.SubItems.Count <= _ColumnIndex Then 'Checks to see if the number of items in ListViewItem2 is <= the column index supplied i.e. no subitem exists at that position
Return 1 'The number of SubItems is <= _ColumnIndex. Returns 1 indicating that it should be moved down
End If
'
'Null item present in a SubItem check
If listViewItem1.SubItems(_ColumnIndex).Text = "" Then 'Checks to see if the subitem at _ColumnIndex in ListViewItem1 is a null
Return -1 'The subitem is a null. Returns -1 indicating that it should be moved up
End If
If listViewItem2.SubItems(_ColumnIndex).Text = "" Then 'Checks to see if the subitem at _ColumnIndex in ListViewItem2 is a null
Return 1 'The subitem is a null. Returns 1 indicating that it should be moved down
End If
ElseIf _SortOrder = SortOrder.Descending Then 'Checks to see if it should perform a descending sort
'
'It should sort in descending order
If listViewItem1.SubItems.Count <= _ColumnIndex Then 'Checks to see if the number of items in ListViewItem1 is <= the column index supplied i.e. no subitem exists at that position
Return 1 'The number of SubItems is <= _ColumnIndex. Returns 1 indicating that it should be moved down
End If
If listViewItem2.SubItems.Count <= _ColumnIndex Then 'Checks to see if the number of items in ListViewItem2 is <= the column index supplied i.e. no subitem exists at that position
Return -1 'The number of SubItems is <= _ColumnIndex. Returns -1 indicating that it should be moved up
End If
'
'Null item present in a SubItem check
If listViewItem1.SubItems(_ColumnIndex).Text = "" Then 'Checks to see if the subitem at _ColumnIndex in ListViewItem1 is a null
Return 1 'The subitem is a null. Returns 1 indicating that it should be moved down
End If
If listViewItem2.SubItems(_ColumnIndex).Text = "" Then 'Checks to see if the subitem at _ColumnIndex in ListViewItem2 is a null
Return -1 'The subitem is a null. Returns -1 indicating that it should be moved up
End If
End If
Return 0 'Returns 0 because no nulls were found
End Function
'''
''' Removes any percentage signs (%) and spaces from the sourceData
''' argument and returns the clean form as a string.
'''
''' The string containing the percentage in its raw form.
''' The percentage value containing just the single
''' data.
''' The function assumes that the argument sourceData
''' is in the form 0.##% (See article on string formatting for more information [todo make link]) where any number
''' of spaces may be present in the string.
''' Using this information, it will strip any spaces and percentage signs (%) from the string and return the
''' result as a string.
Private Function CleanPercentage(ByVal sourceData As String) As String
Return sourceData.Trim(" ", "%") 'Removes any percentage and space characters from the string
End Function
'''
''' Compares two single values and returns their comparison.
'''
''' The first single to compare.
''' The second single to compare.
''' A value indicating the positions of the two singles relative to each other.
'''
'''
''' Return Value
''' Meaning
'''
''' - Less than zerosingle1 is less than single2.
''' - Zerosingle1 is equal to single2.
''' - Greater than zerosingle1 is greater than single2.
'''
'''
Private Function SingleComparer(ByVal single1 As Single, ByVal single2 As Single) As Integer
Dim Result As Single = (single1 - single2) 'Subtracts single2 from single1 and stores the result in Result
'
'Loops while the absolute number of Result < 1.
'Loops because when a single is converted to an integer, if it is < 1 then the decimal
'part is discarded and appears to be the same (i.e. 0 indicates they're the same in a comparison).
Do While Math.Abs(Result) < 1
Result *= 10 'Multiplies Result by 10 to move the decimal point one place to the right
Loop
Return Result 'Returns the result in a form that can be interperated by Integers
End Function
'''
''' Indicates the type of data present when used with the ListViewSortComparer class.
'''
Public Enum SourceDataType
'''
''' Indicates that the type of the data is text (String).
'''
Text
'''
''' Indicates that the type of the data is integers.
'''
Numerical
'''
''' Indicates that the type of the data is dates and/or times.
'''
DateTime
'''
''' Indicates that the type of the data is singles.
'''
[Single]
'''
''' Indicates that the type of the data is percentages.
'''
Percentage
End Enum
End Class