.NET/Java PDF, Tiff, Barcode SDK Library

The ref missing means: pass the object reference that s in the variable called missing, and give the method the option to modify the missing variable so that it refers to some other object, or null on return, if it wants. This is a common pattern with some COM libraries, because it provides a lot of flexibility. But it makes for unpleasant-looking calling code in C# 3.0. However, C# 4.0 makes ref optional when you re using an interop type, which means we can modify the last line of Example 19-4 as shown in Example 19-5.

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var doc = wordApp.Documents.Open(fileName, missing, readOnly, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing);

That s a lot better, but we can go further. C# 4.0 adds support for optional arguments methods can specify the default value to be supplied when the caller omits an argument. On its own, that wouldn t help here, because in general, C# does not allow ref arguments to be optional. However, if it has decided to make the ref optional, as it does in interop scenarios, then it also allows the argument itself to be optional as long as a default value is available. And since the Word PIA provides default values for all the arguments in the method we re using here, we can reduce the call to just the code in Example 19-6.

Listing 1-7. A generated project file ###################################################################### # Automatically generated by qmake (2.00a) to 10. aug 17:06:34 2006 ###################################################################### TEMPLATE = app TARGET += DEPENDPATH += . INCLUDEPATH += . # Input SOURCES += anything.cpp The file consists of a set of variables that are set by using = or extended by using +=. The interesting part is the SOURCES variable, which tells you that QMake has found the anything. cpp file. The next step is to generate a platform-specific Makefile using QMake. Because the working directory contains only one project file, simply type qmake and press Enter. This should give you a Makefile and platform-specific helper files.

var doc = wordApp.Documents.Open(FileName: fileName, ReadOnly: readOnly);

We ve used named arguments here because the arguments are no longer consecutive we only want to supply the first and third, so we name them to make it clear. Named arguments were discussed in 3.

As Example 19-6 shows, the support for optional ref arguments fixes many of the problems that motivated the use of dynamic in 18. C# now offers multiple ways to solve some interop problems, but how should you choose Well, dynamic becomes particularly important when type information lets you down sometimes COM automation APIs don t provide enough type information at compile time, leaving you with properties whose type is nothing more informative than object, at which point, dynamic is usually the best bet. But static typing provides IntelliSense, and can offer better compile-time checks. So it s probably best to stick with static typing until you hit a point where that stops working.

In this example, you will look at converting the data from one format to another, as well as at a two-way binding, where the binding maps in both directions. It isn t a case of changing one control to update another, as you saw earlier with the selection box updating the panel, but of either bound control updating the other. The page looks like Figure 5-5.

Note On GNU/Linux, the result is a single file called Makefile. On Windows, if you use the open-source

Summary

Sometimes you ll need to use components or APIs that were not designed with .NET in mind. You can use COM components and Win32 DLLs from C# thanks to the .NET Framework s interop services. Visual Studio provides additional support specific to ActiveX controls, making it easy to incorporate these into Windows Forms applications. The world of unmanaged code sometimes requires us to work directly with raw memory in an unsafe fashion, and to enable this, C# offers C-style pointers. We strongly discourage you from using them for anything other than interop.

The @ prefix can be especially useful for literal file paths. You don t need to escape all those backslashes. So instead of writing "C:\\some\\path" you can write just @"c:\some\path".

So, we know how to initialize literal strings, which is terribly useful; but what about our other data How do we display an Int32 or DateTime or whatever We ve already met one way of converting any object to a string the virtual ToString method, which Example 10-5 uses.

edition and mingw you get Makefile, Makefile.Release, Makefile.Debug, and two directories: debug and release.

int myValue = 45; string myString = myValue.ToString(); Console.WriteLine(myString);

This will produce the output you might expect:

decimal myValue = 45.65M; string myString = myValue.ToString(); Console.WriteLine(myString);