If the property is a value type, cast to a nullable inside the lambda like so:
Employee.NullSafe( e => (double?) e.Sallary )

To remind the users of this, rewrite the extension methods as follows:

public static TOut NullSafe(this TIn obj, Func memberAction ) where TIn : class where TOut : class
{ return ReferenceEquals(obj, null) ? null : memberAction(obj); }

public static TOut? NullSafe(this TIn obj, Func memberAction ) where TIn : class where TOut : struct
{ return ReferenceEquals(obj, null) ? null : memberAction(obj); }

public static TOut NullSafe(this TIn? obj, Func memberAction ) where TIn : struct where TOut : class
{ return obj.HasValue ? memberAction(obj.Value) : null; }

public static TOut? NullSafe(this TIn? obj, Func memberAction ) where TIn : struct where TOut : struct
{ return obj.HasValue ? memberAction(obj.Value) : null; }

It might seem possible to get rid of the requirement to cast to Nullable through some generic magic. It almost is. Unfortunately, the compiler complains when two generic functions differ only in their generic type constraints and return value. But you can add the following extension methods to the mix:

public static TOut? NullSafeV(this TIn obj, Func memberAction ) where TIn : class where TOut : struct
{ return ReferenceEquals(obj, null) ? (TOut?)null : memberAction(obj); }

public static TOut? NullSafeV(this TIn? obj, Func memberAction ) where TIn : struct where TOut : struct
{ return obj.HasValue ? memberAction(obj.Value) : (TOut?)null; }

The correct way to handle both reference and nullable types is the following:

public static TOut NullSafe(
this TIn obj,
Func memberAction ) where TIn : class
{
return ReferenceEquals(obj, null) ? default(TOut) : memberAction(obj);
}

public static TOut NullSafe(
this TIn? obj,
Func memberAction ) where TIn : struct
{
return obj.HasValue ? memberAction(obj.Value) : default(TOut);
}

public static TOut NullSafe(this TIn obj, Func memberAction)
{
//Note we should not use obj != null because it can not test value types and also
//compiler has to lift the type to a nullable type for doing the comparision with null.
return (!EqualityComparer.Default.Equals(obj, default(TIn))) ? memberAction(obj) : default(TOut);

}

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Thanks mate. I believe the kinnect gesture recognition database idea is a good one and is certainly worth spending some time. Unfortunately I have not been able to work on it as yet. If you are interested, go ahead and kickstart the project and let me know about it.

Nice blog. I will post a link on my tumblr page.

Non mathematical way is to say, well a chicken and half lays three eggs in three days, so a chicken lays two eggs in three days.