Category Archives: c#

How to insert blank rule (<br />) from C# code

Once in a while I have to develop custom user controls that require blank rules in them. Almost always I think again: ‘I should have blogged about it, would have saved me lots of time searching’ :) … Well, no more, because here it is…

Many people using blank rules in C# code, use the following commands:

var brControl1 = new HtmlGenericControl { InnerHtml = "<br />" };
var brControl2 = new HtmlGenericControl("br");

However, brControl1 also prints a <span> tag and brControl2 prints <br></br>. Both options are not really useful. You should take notice of the fact that the HtmlGenericControl is not meant to be used for anything else than span, body, div and font (what is designed for ‘as the word goes’).  The way to go when printing a blank rule is:

var brControl3 = new LiteralControl("<br />");

This actually prints exactly what you would like it to print, namely <br />. Hope this helps you too :) ! BTW, if you are using the HtmlTextWriter class, you can also use the WriteBreak() function if you like.

Solution: The operation could not be completed. Invalid FORMATETC structure

This morning I ran into a ASP.NET bug in Visual Studio. Dragging a custom server control on an aspx file was not possible since I had ‘an invalid FORMATETC structure’ (what the …. is that?!). The message box alerting me something is really really wrong is this one:


Trying to solve the bug, I  found the following attribute to be the problem: [ToolboxItem(true)]. Just delete the attribute, rebuild the application and the problem/bug disappears!

Good luck! Happy coding!

Logging duration with System.Diagnostics.StopWatch instead of using DateTime.Now

Still using two DateTime.Now calls to determine the duration of a certain call execution, like beneath?

DateTime start = DateTime.Now;
double secondsToLog = (DateTime.Now - start).TotalSeconds;

This is not at all necessary: using the StopWatch class. The StopWatch class is more efficient than any other solution provided or created in .NET since it uses low-level API calls and supports a high-resolution performance counter (when there is hardware and software support).

Stopwatch watch = new Stopwatch();
double secondsToLog = watch.Elapsed.TotalSeconds;

Dutch social security number check

For a Dutch customer I currently work for, I dealed with an incorrect social security number check (in Dutch: elfproef voor BSN’s/burgerservicenummers). After checking out the Internet for the correct definition of Dutch social security numbers (e.g. Burgerservicenummer – Wikipedia), I created the next check in C#:

string cleanBsnNr = bsnNr.Trim().Replace(".", "");

// A BSN consists of 9 characters ...
if(cleanBsnNr.Length != 9) return false;

// ... all being numeric and not resulting in a 0 when converted to a number ...
long l;
if(!long.TryParse(cleanBsnNr, out l)) return false;
else if(l == 0) return false;

// ... the number must be validatable to the so-called 11-proof ...
long total = 0;
for(int i = 1; i <= 9; i++)
    // 11-proof voor BSN's: (9*A + 8*B + 7*C + 6*D + 5*E + 4*F + 3*G + 2*H + (-1*I)) % 11 == 0
    int number = Convert.ToInt32(cleanBsnNr[i - 1].ToString());
    int multiplier = 10 - i;
    if(i == 9) multiplier = -1 * multiplier;

    total += number * multiplier;

// ... not result in a 0 when dividing by 11 ...
if(total == 0) return false;

// ... and not have a modulo when dividing by 11.
return total % 11 == 0;

Good luck when you should build one for yourself. Checking your own built check can be done using this website with generated BSN’s (or your own, of course) by Menno Wilmans.