Sorting a List based on an ArrayList within a custom Object

Question

I am using a list to keep track of a number of custom Row objects as follows:

Public Rows As List(Of Row)()

Row has 2 properties, Key (a String) and Cells (an ArrayList).

I need to be able to sort each Row within Rows based on a developer defined index of the Cells ArrayList.

So for example based on the following Rows

Row1.Cells = ("b", "12")
Row2.Cells = ("a", "23")

Rows.Sort(0) would result in Row2 being first in the Rows list. What would be the best way of going about implementing this?

Thanks

Mitchel Sellers · Accepted Answer · 2010-05-24 14:47:37Z

1

If you implement IComparable on your Row object, you can define a custom comparison process to be able to do the sorting that you desire.

Here is an intro article to get you started.

answered May 24, 2010 at 14:47

Mitchel Sellers

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2 Comments

Matt Weldon Over a year ago

Thanks for that, IComparable works a treat with a little bit of tweaking to my Row object.

Mitchel Sellers Over a year ago

Glad it helped, the first few times it is a bit tricky, but very helpful for these custom sort items

Tim Schmelter · Accepted Answer · 2010-05-24 17:48:30Z

Its similar to a DatRow with it's Columns, so you can alternative(to the IComparable solution) use the sort-ability of a DataView:

Consider creating a DataTabale on the fly with its columns as your cells. For example:

Dim rows As New List(Of Row)
Dim row = New Row("Row 1")
Dim cell1 As New Row.Cell("b")
Dim cell2 As New Row.Cell("12")
row.Cells.Add(cell1)
row.Cells.Add(cell2)
rows.Add(row)
row = New Row("Row 2")
cell1 = New Row.Cell("a")
cell2 = New Row.Cell("23")
row.Cells.Add(cell1)
row.Cells.Add(cell2)
rows.Add(row)

Dim tbl As New DataTable()
''#are the cell count in every row equal? Otherwise you can calculate the max-count
Dim cellCount As Int32 = 2 ''#for example
For i As Int32 = 0 To cellCount - 1
    Dim newCol As New DataColumn("Column " & i + 1)
    tbl.Columns.Add(newCol)
Next
For rowIndex As Int32 = 0 To rows.Count - 1
    row = rows(rowIndex)
    Dim newRow As DataRow = tbl.NewRow
    For cellIndex As Int32 = 0 To row.Cells.Count - 1
        Dim cell As Row.Cell = row.Cells(cellIndex)
        newRow(cellIndex) = cell.value
    Next
    tbl.Rows.Add(newRow)
Next
Dim view As New DataView(tbl)
view.Sort = "Column 1"
''#you can use the view as datasource or other purposes

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