David Truxall

The Clipboard Ring Rules!

ADO.Net 2.0 Presentation on January 20th

VSTO Excel ListObject Bug

Generics and Enums or Enum.TryParse

I have a case where the user is entering strings into the application, and I have to match that string with the values from a given Enum. Normally that is not too difficult of a task, just convert the enum item to a string and compare, but in this instance I have a bunch of enums to do this with, so I didn't want to write a separate function for each enum type. So I figured generics might provide a solution and here is what I came up with, which is loosely based on the idea of int.TryParse:

/// <SUMMARY>
/// Takes a string that represents an enum member 
///   and returns the enum member
/// </SUMMARY>
/// <TYPEPARAM name="T">An Enum</TYPEPARAM>
/// <PARAM name="input">
///  The string that is the enum member name, case does 
///    not matter
/// </PARAM>
/// <PARAM name="returnValue">
/// The value from the enum that matches the string, or the 
/// first value of the enum /// </PARAM>
/// <RETURNS>
/// True when there is a match, false when not
/// </RETURNS>
/// <REMARKS>
/// - When no match the first item in the enum is returned
/// - The where clause attempts to constrain the input of T 
///   at compile time to be an Enum
/// </REMARKS>
private bool GetEnumValue<T>(string input, out T returnValue) 
             where T : struct, IComparable, IFormattable, IConvertible
{
    if(Enum.IsDefined(typeof(T), input))
    {
        returnValue = (T)Enum.Parse(typeof(T), input, true);
        return true;
    }
    else //input not found in the Enum, fill the out parameter
         //  with the first item from the enum
    {
        string[] values = Enum.GetNames(typeof(T));
        returnValue = (T)Enum.Parse(typeof(T), values[0], true);
        return false;
    }
}

Awesome IIS Resource

Comboboxes and Double-Clicks

The standard combobox control doesn't support the double-click event, as it is actually a combination of more than one control itself. In my case, I am using the combobox in simple mode with a textbox at the top and a permanently open list directly below the textbox. I needed for the listbox below to respond to the user double-clicking a list item. I found a great solution in a Usenet post by Jacques Bourgeois in microsoft.public.dotnet.framework.windowsforms.controls. Essentially the code simulates a double-click using the single-click event and a timer control.

Declare a timer control in your class, and in the load event of the form instantiate the timer set the interval of the timer to the interval of the double-click as set in the user's system:

In the event handler for the timer, set the code to stop the timer:

Add code to the single-click event handler to handle the double-click. When the event handler fires, if the timer is not enabled, start the timer (the first click). If the timer is enabled, a previous click has occurred within the system set interval for a double-click. This must be the second click of the double-click, so do whatever you needed the double-click to do and then disable the timer for the next single-click event.

C#, VSTO 2005 and ActiveCell.Offset

Just a quick tidbit about using the Excel object model and C# in VSTO 2005. ActiveCell.Offset (as we know it in VBA, and even VB.Net) is not there in exactly the same way with C#. The syntax for C# is:

ActiveCell.get_Offset(1,1).Value2 = 22

And of course you need to use Value2 instead of Value, it's not like there is any choice there anyway.

SelfSSL and Site ID

SelfSSL is a tool found in the IIS 6.0 Resource Kit. It allows you to generate SSL certificates for a development environment. In all the instructions for using SelfSSL, it describes one of the parameters as "Site ID", where the default value=1, which is the default web site installed on the computer. The Site Id parameter is essentially telling SelfSSL which web site to install the certificate into. Well, if you have multiple web sites, then the default site id is useless. You need the Site Id of the web site where you want the certificate installed. Of course the documentation does not spell this out, and as a non-Admin the Site Id was not an intuitive term for me. But I found that there is a script you can run from the command-line called iisweb.vbs using the /query switch. That will tell you the Site Id. Seeing that, then I realized that the IIS log file folders (in windir\System32\logfiles\) are named according to the Site Id.

Anyway, creating a second certificate for a different site on the same IIS using SelfSSL messes up the SSL cert of first site. This is a known issue apparently, and David Wang has a great post on this problem. The comment further down by Paul Carrig is most useful, as he points out there is a workaround for the SelfSSL and multiple site issue. So I actually found two workarounds:

1. The technique described by in the aforementioned post:
   1. Install the cert in the first site
   2. Export it to a .pfx file
   3. Install the cert in the second site
   4. Remove the cert from the first site
   5. Re-Import the cert to the first site using the .pfx file
      
      or
      
2. Install the cert in the first site, and export it to a .pfx file. Then import that to the other sites. The down side to this is that the certificate is even less valid for the second sites as now it has an untrusted publisher (me!) and the site name is not a match. The prompt is essentially the same, but in our case one site contains web services which will throw an error if the prompt comes up at all (as it should). The workaround for that is to install the certificate on the client computers as well, which is an acceptable problem for a development enviroment.