nullable

So, I asked a question this morning, which I did not phrase correctly, so I got a lot of responses as to why NULL compared to anything will give NULL/FALSE. My actual question was, what is the time honored fashion in which db guys test inequalities for two columns that can both be NULL. My question is the exact opposite of this question . The requirements are as follows, A and B are two columns: a) if A and B are both NULL, they are equal, return FALSE b) if A and B are both not NULL, then return A<>B c) if either A or B are NULL, they are not equal, return TRUE Depending on the data type and

I am writing algorithms that work on series of numeric data, where sometimes, a value in the series needs to be null. However, because this application is performance critical, I have avoided the use of nullable types. I have perf tested the algorithms to specifically compare the performance of using nullable types vs non-nullable types, and in the best case scenario nullable types are 2x slower, but often far worse. The data type most often used is double, and currently the chosen alternative to null is double.NaN. However I understand this is not the exact intended usage for the NaN value,

why is typeof int? an Int32 int? x = 1; Console.WriteLine(x.GetType().Name); If it is okay then what's the use of Nullable.GetUnderlyingType ? Calling GetType() boxes your variable. The CLR has a special rule that Nullable<T> gets boxed to T . So x.GetType will return Int32 instead of Nullable<Int32> . int? x = 1; x.GetType() //Int32 typeof(int?) //Nullable<Int32> Since a Nullable containing null will be boxed to null the following will throw an exception: int? x = null; x.GetType() //throws NullReferenceException To quote MSDN on Boxing Nullable Types : Objects based on nullable types are

For my own implementation of an Equals() method, I want to check a bunch of internal fields. I do it like this: ... _myNullableInt == obj._myNullableInt && _myString == obj._myString && ... I would assume, that this compares the values, including null, for equality not the object address (as a reference euqality compare operation would) because: It is said so for "predefined value types" in this MSDN doc here . I assume Nullable<int> is such a "predefined value type" because of it is in the System Namespace according to this MSDN doc . Am I right to assume that the VALUES are compared here?

I am using an ADO.NET Entity-Framework ObjectContext to access my data store. I want the if values are set with empty strings, they should automatically become null. Sterling Nichols If your using Entity Framework 4, you can use T4 templates to accomplish this. Just place this in the getter of each string property in your .tt template file, and it will replace empty strings with null and automatically trim strings. No need to use reflection. <#+ if (primitiveProperty.TypeUsage.ToString().Split('.').Last() == "String") { #> if (value == "") value = null; else value = value.Trim(); <#+ } #> I