Thursday, March 27, 2008

Finding the Temp Directory and Getting Temporary Filenames in VB.NET and C#

In a previous post, I showed how to get special directories like My Document and System32, but I also need to get the location of the Windows Temp directory and this is not covered by the SpecialFolders property (see previous post for more info on it).

Getting the Temp folder is just as simple, but it is done with a different property:

tempPath = System.IO.Path.GetTempPath

You can also generate temp filenames with:
tempFilename = System.IO.Path.GetTempFileName

Sunday, March 23, 2008

Launching Excel to view Files from VB.NET

Launching Excel from VB.NET to view a file (.xls, .csv, .etc) has a seemingly simple solution:


However, this simple solution has a problem. After Excel is running, it does not respond to this type of command anymore. Excel has to be closed (killed) before you can successfully call Start again with any file that is associated with Excel.

I see several different approaches to this problem:

There is also a totally different approach using Excel's automation to open the file:

Exporting ListView to CSV File in VB.NET

I have posted an article on copying a ListView to the Windows Clipboard, but I have also found it useful to export a ListView directly to a .CSV file (comma separated value file). The process to go from a ListView to the clipboard or to a CSV file is similar.

There are number of rules for creating a CSV file. Here is a good place to look if you want to see them all. I have simplified the process to a few rules that will work for most cases. I put quotes around all values and column names. Technically, this is not required, but by putting them around all cases eliminates the need to determine if you need them or not. I also replace any quote in the data with a double quote.

Public Function ExportListViewToCSV(ByVal filename As String, ByVal lv As ListView) As Boolean


' Open output file
Dim os As New StreamWriter(filename)

' Write Headers

For i As Integer = 0 To lv.Columns.Count - 1
' replace quotes with double quotes if necessary
os.Write("""" & lv.Columns(i).Text.Replace("""", """""") & """,")


' Write records
For i As Integer = 0 To lv.Items.Count - 1
For j As Integer = 0 To lv.Columns.Count - 1
os.Write("""" & lv.Items(i).SubItems(j).Text.Replace("""", """""")+ """,")




Catch ex As Exception
' catch any errors
Return False
End Try

Return True

End Function

You may want to get the file name from the user and automatically open the file in Excel too. Here is an example of how to do that:

Public Sub TestExportToCSV()

Dim dlg As New SaveFileDialog
dlg.Filter = "CSV files (*.CSV)|*.csv"
dlg.FilterIndex = 1
dlg.RestoreDirectory = True

If dlg.ShowDialog = Windows.Forms.DialogResult.OK Then

If ExportListViewToCSV(dlg.FileName, ListView1) Then


End If

End If

End Sub

Saturday, March 15, 2008

Creating Events for a Class in VB.NET

I have found the ability to create and raise events in a class to be a very useful feature of .NET. It also turns out to be very easy to implement.

I could provide an example here, but I will instead point to a good example I have found:

Comparing Objects (Pointer Equality) in VB.NET

It was not readily obvious to me how to compare references (pointers) to an object to see if both references are pointing to the same object in VB.NET.

The specific example that raised this question for me was the need to see if a reference pointing to a ToolStripMenuItem object was in a list of ToolStripMenuItem objects:

Private m_itemList As New Generic.List(Of ToolStripMenuItem)
Private Function GetItemPosition(ByVal item _
As ToolStripMenuItem) As Integer

For i As Integer = 0 To m_itemList.Count - 1

' If m_itemList(i)=item Then ' This doesn't work

If Object.ReferenceEquals(m_itemList(i), item) Then ' This does

Return i

End If


Return -1
End Function

You can't just directly compare the references. You will get an error message that says: Operator '=' is not defined for types 'System.Windows.Forms.ToolStripMenuItem' and 'System.Windows.Forms.ToolStripMenuItem'. But there is a simple, if not readily obvious to me, solution. Just use the Object.ReferenceEqual method:

If Object.ReferenceEquals(item1, item2) Then
End If

Friday, March 14, 2008

Tooltips in VB.NET

One nice feature of VB.NET is the ease in which you can implement tooltips for any Control on the desktop (unfortunatley not for .NET CF, see here).

Define a global variable for the tooltip object:

Dim g_toolTip As ToolTip = Nothing

Initialize the tooltip object. There are several settings that can be initialized too:

g_toolTip = New ToolTip()
g_toolTip.AutoPopDelay = 5000
g_toolTip.InitialDelay = 1000
g_toolTip.ReshowDelay = 500
g_toolTip.ShowAlways = True

When you are ready to display a tooltip, you must specify the control that the tooltip is associated with (ctrl in my example). The control is any object derived from Control, so if you make your own .NET control (deriving it from the Control base class), it can be associated with the tooltip. You can also use existing controls like Button and PictureBox.

g_toolTip.SetToolTip(ctrl, "tooltip text")
g_toolTip.Active = True

This functionality is actually documented pretty well in the Microsoft documentation. There are also C# example and detailed descriptions of the options like AutoPopDelay.

Sunday, March 9, 2008

Color Selection Dialog in VB.NET

The Color Selection Dialog for VB.NET (and C# would be similar) is fairly easy to do if you have and example:


Dim colorValue As Color = Color.Red

Dim dlg As New ColorDialog

dlg.Color = colorValue

If dlg.ShowDialog() = DialogResult.OK Then
colorValue = dlg.Color
End If

For VB6, here is one way to do it:

Monday, March 3, 2008

Tooltips with the .NET Compact Framework

I have been looking for a way to support Tooltips in .NET CF like I do on the desktop with the Tooltip object. There must be something better out there that I just haven't come across. Please post a comment if you know of something.

This is the only thing I have found that is reasonably close to what I want, but it is still not what I really want (wich is the Tooltip object from the desktop):

Here is the full posting from the Windows Mobile Team Blog:

The source code for the control is:

The example project that uses it is: