Improper exception handling demonstration

[jinek]

On this page https://docs.microsoft.com/en-us/dotnet/api/system.windows.controls.contentcontrol.contenttemplateselector?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DEN-US%26k%3Dk(System.Windows.Controls.ContentControl.ContentTemplateSelector);k(VS.XamlEditor);k(SolutionItemsProject);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.7)%26rd%3Dtrue&view=netframework-4.7.1
There is an example with following code:
catch { return null; }
The behavior of this code does not match the expectations. For example, catched OutOfMemoryException or NullReferenceException do not mean we should provide empty Template. Better to rewrite that as
'catch(FormatException)
{
return null;
}'

[mairaw]

Thanks @jinek, that's a good suggestion. Do you wanna try to submit a PR for this? Otherwise, we can handle it.

[jinek]

Yes, would be great. Let me do this.

[jinek]

@mairaw May I also refactor it a little bit, like removing Application.Current.MainWindow; and adding numberTemplate and largeNumberTemplate properties instead.

Also what I see is code does not match the behavior description. There is nothing said about cases when "null" template will be used. As I see it is better to remove some null returns instead of DataTemplate. If we want to explain some exception handling technique it's better to rethrow the exception ( https://github.com/jinek/docs/blob/52d3ef051f577fe16347082413a89d1dbb19ac6a/samples/snippets/csharp/VS_Snippets_Wpf/ContentControlTemplateSelector/CSharp/Window1.xaml.cs ) or not to catch it at all as exception handling is out of the example subject:

In this way (picture demonstrated) reader can get information more easily as it shows twice less code.

[mairaw]

Feel free to refactor and will review your suggestions. Thanks @jinek!

[mabumann]

I propose that the class name is modified from NumderDataTemplateSelector to NumberDataTemplateSelector.

[mairaw]

Yes, @mabumann. @jinek is doing that already on the PR #4016. I just have a final question to him on that PR before we finish this issue.

[jinek]

I will make changes to VB also in a few days

[mairaw]

Thank you @jinek! I was going to tell you I was going to do the VB part today, but we can wait a few days if you wanna finish it. Either way works. Thanks so much!