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.NET Forum / Languages / VB.NET / March 2008RE: Nullable(Of Integer) question
I am new to Nullable types. Let's say that I have a variable as follows: Dim iID As Nullable(Of Integer) Now, let's say that I have code that either needs to assign an integer value to iID or have it be NULL. For simplicity, let's use... If (True) Then iID = 12 Else iID = Nothing End If At this point, if iID = Nothing was executed, iID = 0 and iID.HasValue returns True! What do I assign to iID such that iID.HasValue will return False? > I am new to Nullable types. > [quoted text clipped - 15 lines] > iID.HasValue returns True! What do I assign to iID such that > iID.HasValue will return False? Can't reproduce it. After assigning Nothing, iId.Hasvalue returns false. Armin Oops...I figured out what the problem was. I was assigning the value via a function that was returning an Integer. In certain circumstances, I was returning Nothing, which ultimately returned ZERO (0). I just had to change the function so that it returned a Nullable(Of Integer). Silly me... Bob, I am always curious why people will use what you are doing, a nullable integer is in fact a worse thing from the past. What is your reason? (Be aware that a integer that is null, has nothing to do with the value type DBNull.Value which can be inside an object) Cor >I am new to Nullable types. > [quoted text clipped - 14 lines] > returns True! What do I assign to iID such that iID.HasValue will > return False? This is for example used in LINQ to SQL to handle nullable columns. Yes I know this is not the same thing but just a "representation", I believe we already had this discussion without understanding much each other.... Likely more usefull for date columns as they can usually hold a date for a future event in which case those columns are made nullable than for any other data type... -- Patrice > Bob, > [quoted text clipped - 7 lines] > > Cor > Bob, > > I am always curious why people will use what you are doing, a nullable > integer is in fact a worse thing from the past. > > What is your reason? I use Nullable(Of Integer) for variables that will store foreign key references to other tables. So, let's say that I have a class called LoanApplication, with a property called fkDeclinedByUserID. This property must either be NULL, or have an integer value corresponding to the primary key field of a User record. In my code that does the DB update or insert, I check to see if fkDeclinedByUserID.HasValue is True. If it is, I pass in the integer to the stored procedure parameter; otherwise, I pass in System.Convert.DBNull. I use a table whith a field that is relation whith another table I use a from with textboxs binding to a dataset When I want to clear the value of this field it receive the "" value and it can be save in the bd because the relational table not have "" record, I need to give null value before update the record, how can i do? Thanks Sorry my English >> Bob, >> [quoted text clipped - 11 lines] > True. If it is, I pass in the integer to the stored procedure > parameter; otherwise, I pass in System.Convert.DBNull. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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