29 November 2011

Error during serialization or deserialization using the JSON JavaScriptSerializer

Today one of the internal web applications that we have wouldn't run properly on my development machine (it works fine on the production server). When opened it would produce the following exception:

Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.

It seems that the production server has a higher maxJsonLength value in its machine.config than my development machine. To solve this problem, add the following in your web.config.

22 November 2011

The Null coalescing operator

It seems that a lot of people do not know of the existence of this handy little operator, so I decided to put it up here, so it may help somebody clean up their code.

Have you ever had a Nullable<...> type which you needed to read to a regular value type, but needed a "default" value for when it was NULL, as the regular value type cannot handle it?
Chances are, you've written it in one of the following ways:

int? i = null; // please note that Nullable<int> is the same as int?
int a;
if(i.HasValue) // equal to: if(i != null)
  a = i.Value;
  a = -1;


int a = i.HasValue ? i.Value : -1; // This is already a bit shorter!

But using the NULL coalescing operator, you can simply write:

Entity Framework: duplicate rows in resultset from a view

After including a view I have in my database in an Entity Framework data model, I noticed that for some strange reason, the result was showing duplicates. When a set should have for instance 10 different rows, it might contain only 4 different rows, some of which were duplicated so it was still a total of 10 rows.
The view itself showed the correct results, but when called from code using the Entity Framework, it once again showed the wrong results.
After some testing I found out that the rows that were duplicated, were rows that shared certain values with the rows that were replaced by it. After checking this in my Entity Model, I soon found at that the Entity Model has a strange way of handling rows with equal primary key values.

I'll try and explain my findings:

Windows Task Scheduler error 2147942667

If you have created a task within Windows Task Scheduler, you might encounter a task that does not run properly. When you look into the history of the task, you might find the following error message:

Task Scheduler failed to start instance "<guid value>" of "<task name>" task for user "<user name>" . Additional Data: Error Value: 2147942667.

The reason for this error is the fact that you have put quotes (") around the value in Startup Path. Strangely, the executable may have quotes surrounding it (e.g. "C:\Path to\Executable.exe"), but the Startup Path may not, even when there are spaces in the Path (which makes the use of quotes for the executable necessary).

Remove any quotes you have in the Startup Path value and try again.

See also this Microsoft Support Article:
Windows Vista onwards scheduled tasks fail to run if the path in "Start in (Optional)" field has quotes