LINQ: ‘Week Commencing’ TreeNodes

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I needed a way to create a TreeView in VB.NET that contained a node for each month of the year, and each month node had to contain a node for each Monday within that month. A ‘Week Commencing’ type of view. This type of problem always seems better solved with LINQ, so here’s how I did it:

Private Function GenNode() As TreeNode

        Dim rootNode As New TreeNode("Week Commencing")

' Create a list containing every date of the year
        Dim dateList As New List(Of Date)
        Dim dateIterator As New Date(Year(Now), 1, 1)
        Do Until dateIterator.Year <> Year(Now)
            dateList.Add(dateIterator)
            dateIterator = dateIterator.AddDays(1)
        Loop

' Now, using LINQ, create the TreeNodes
        Dim t = From d In dateList Group d By m = d.Month Into Group Select
            New TreeNode(MonthName(m),
                (From d1 In dateList Where d1.Month = m And d1.DayOfWeek = DayOfWeek.Monday Select New TreeNode(d1.ToString("dd-MM-yyyy"))).ToArray) Distinct

        rootNode.Nodes.AddRange(t.ToArray)

        Return rootNode

    End Function

For more information on LINQ, see the following link 🙂

http://msdn.microsoft.com/en-us/library/vstudio/bb397926.aspx

SQL Trim with Alternative Characters

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SQL Trim UDF

.NET strings have a method that allow you to trim characters from the beginning and end of a string. There is also a SQL trim function, but you can only trim the space character, unfortunately you cannot specify which character you want to trim. I sought to rectify this with a UDF:

CREATE FUNCTION TrimSingleChar
(
-- Add the parameters for the function here
@needle nchar(1),
@haystack as nvarchar(max)
)
RETURNS nvarchar(max)
AS
BEGIN
DECLARE @pos as int -- variable to hold the position of @needle

-- Check whether @needle appears at the start of the string
SELECT @pos = CHARINDEX(@needle,@haystack,0)
IF @pos = 1
BEGIN
SELECT @haystack = SUBSTRING(@haystack,2,LEN(@haystack) -1)
END

-- Reverse the string
SELECT @haystack = REVERSE(@haystack)

-- Check again whether @needle appears at the start of the string
SELECT @pos = CHARINDEX(@needle,@haystack,0)
IF @pos = 1
BEGIN
SELECT @haystack = SUBSTRING(@haystack,2,LEN(@haystack) -1)
END

-- Reverse the string to back how it was, and return it
RETURN REVERSE(@haystack)

END
GO

Unfortuantely at the moment this function will only trim a single instance of @needle from the beginning and end, but at the moment that’s all I need.

As .NET has native functions available to perform the above task, a better option would be to use a SQL CLR function. That’s beyond the scope of this article, however. Maybe next time! For more information about SQL CLR functions, you can check out more at this link: http://msdn.microsoft.com/en-us/library/ms131077.aspx

For more information about SQL UDF functions, you can read more here: http://technet.microsoft.com/en-us/library/aa214363(v=sql.80).aspx

OpenChronos Compiliation in Windows

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OpenChronos Compiliation

Ok, it would appear that while the previous fix helped the entire process along a little, I still  could not get OpenChronos to build.

And now I’ve run out of time, as I need to get back to music!