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More on Comparing Nullable Types and Generics

Pete Brown - 09 September 2005

If you recall from yesterday's blog entry, I was having some problems trying to find a way to compare some generics which may contain nullable types. My thanks go to Dinesh and his colleagues for solving this problem for me.

Here's the new code; it's much simpler than the old code.

  protected void SetProperty<T>(ref T currentPropertyValue, T newValue)
   Comparer<T> comparer = System.Collections.Generic.Comparer<T>.Default;

   if (comparer.Compare(currentPropertyValue, newValue) != 0)
    currentPropertyValue = newValue;

Simple! Thanks again, Dinesh!

Now, the question of figuring out how to tell if a generic is nullable becomes just an academic pursuit, rather than a critical problem. I'm still interested in a solution to that, so if you have one, please feel free to comment.

[ As an aside, Dinesh also pointed out that anonymous users could not post comments to my blog. That is now fixed. ]

Update: Dinesh had this to say:

I am glad I could be of some help and thanks again from trying the CTP. Here is how you can check for a Nullable type – it is a bit more complex but actually cleaner than using INullableValue as a "marker" interface.

if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>)) {…}

I will add this to my blog for broader distribution.


Dinesh Kulkarni

Program Manager, Visual C#

Thanks again Dinesh! I owe you a drink or something at the PDC next week :)

posted by Pete Brown on Friday, September 9, 2005
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