We were dealing with a datasource of (int? id, string value) pairs in LINQ. The data has originated from a database where id is unique field. In the program this datasource had to be seen as a dictionary, so we have written a code like this:

var dictionary = CreateIDValuePairs().ToDictionary(item => item.ID, item => item.Value);

That was too simple-minded. This code compiles but crashes at runtime when there is an id == null.

Well, help warns about this behaviour, but anyway this does not make pain easier.

In our opinion this restriction is not justified and just complicates the use of Dictionaty.