∞

This page lists some of the more popular “ASP.NET 2.0 Tips, Tricks, Recipes and Gotchas” posts by Scott Guthrie

For those of you working with FDF I recommend using iTextSharp rather than Acrobat FDF Toolkit

The iText# (iTextSharp) is a port of the iText open source java library written entirely in C# for the .NET platform. iText# is a library that allows you to generate PDF files on the fly. It is implemented as an assembly.

On contrary Acrobat FDF Toolkit is available as an ActiveX component in your .net application and thus involves COM Interoperability.

Check out a nice sleek introductory article about .net here

Well in .net 1.1, obviously NO! “int” is a value type and “null” cannot be assigned to a value type. Well what to do then? Interestingly in .net 2.0 we can have nullable value types by simply declaring a variable as:

int  x = null;        //Cannot convert null to ‘int’ because it is a value type

int? x = null;        //Allowed

Pretty cool way of declaring nullable value types. Wait there’s a bit more to add here. How would you check if some variable has a value of “null” or not?

You might be thinking of writing something like:

Console.WriteLine((x != null? 1 : 0));

How about writing it like this:

            Console.WriteLine((x ?? 0));.net 2.0 introduces a new operator “??” which is called as “null coalescing operator”. As you can see it’s a very powerful operator as it provides you the “null checking abilities” in your code. It works by the following rule of thumb: “Return the first value if not null otherwise simply return the second value if null”. MSDN describes it as “The ?? operator returns the left-hand operand if it is not null, or else it returns the right operand.”

Another interesting thing to note is that if you have a nullable type and you want to assign it to a non-nullable type then you need to make use of the “??” operator. Otherwise the compiler will generate an error. For example if I write as:

int y = x; //Cannot implicitly convert type ‘int?’ to ‘int’. An explicit conversion

                        exists (are you missing a cast?)

Now if you use the cast here and the nullable type is undefined i.e. null then an InvalidOperationException exception will be thrown.