Exploring the Possibilities

Using IntelliSense is also a way to explore all the possibilities that every contemporary computing platform offers.

In former days, you had to study the possibilities in manuals or books. Some of them were capable enough to cover almost all the questions a programmer had. Today, however, there are so many possibilities that even a 1000-page book cannot show them all.

You still need books (definitely this one!) to give you reliable and systematic instruction so you can understand the principles, but you will probably want to explore further possibilities not mentioned there. IntelliSense is a tool that can show you many of them.

Examples

Are you looking for possibilities of how you can manipulate text? Create a variable of the string type and enter its name followed by a dot (see Figure 14-1).

You can find even more possibilities when you directly enter string followed by a dot (see Figure 14-2).

Are you looking for actions you can perform with dates? Enter the DateTime variable and then a dot (see Figure 14-3).

Like with text, you can enter DateTime and a dot and get some tips on what might be useful to use (see Figure 14-4).

Note

The list of possibilities that IntelliSense offers you can be narrowed down using the icons at the bottom of the list. Click an appropriate icon if you want to see just properties, just methods, and so on.

Keyboard Shortcuts

It happens sometimes that you do something and IntelliSense disappears. In this case, you may find Ctrl+J or other keyboard shortcuts useful. To get a list of them, in Visual Studio’s menu bar, select Edit ➤ IntelliSense ➤ List Members (see Figure 14-5).

docs.microsoft.com

The Web at http://docs.microsoft.com is the best place to start looking for anything concerning C# and other Microsoft technologies (see Figure 14-6). On the page, click “Documentation” and then go directly to “C#”.

Search

You can work with the documentation site using the links provided. However, more frequently you are going to search for specific things. For example, enter Console class in the search field and press the Enter key (see Figure 14-7).

The link you are interested in is often the first one returned (see Figure 14-8).

Specific Class Page

After clicking the correct link, you will find all the things about a specific class, such as Console in this example.

When I am getting acquainted with some class I do not know yet, I usually look for “Common Operations” and “Remarks” sections, which cover basic information about the class usage and entry points to further details (see Figures 14-9 and 14-10).

Common Search

To conclude this section about documentation, note that you can perform your searches outside of the Microsoft documentation site, too. Simply use your favorite web browser to search.

However, contrary to a documentation site search, a common search displays irrelevant results more frequently. To compensate for this, you can refine your query using the programming language name, such as entering Console class C# in your favorite web browser’s search field.

Project

It is best to try all the tools in practice, so please open the “Treating incorrect input” project in Visual Studio from Chapter 8. The program adds two numbers and treats possible input errors using try-catch.

Stepping Through the Code

A computer works so fast that it is impossible to follow it with its gigahertz speed. That is why it’s often helpful to step through the code, which forces the computer to execute one statement at a time, upon your command.

Go to your opened “Treating incorrect input” project and launch it using the F10 key instead of the usual F5. Of course, selecting the Debug ➤ Step Over menu does the same thing (see Figure 14-11).

The individual program statements are now being executed one at a time whenever you press F10. All the while, using a yellow arrow and yellow background, the development environment denotes the statement that is to be executed in the next step.

Now just play with the stepping. Try the case when the user enters correct data and also the case of wrong input. The IDE will show you how try-catch or anything else works. This allows you to see how the program runs with your own eyes.

Breakpoints

I have covered what to do if you do not want to step through your code after you have passed the point you are interested in. There is another situation. Say you do not want to do any stepping before you get to the place of interest. In that case, you can use a breakpoint.

Click the statement where the computer is to stop and press F9 (alternatively, right-click and choose Breakpoint ➤ Insert Breakpoint). The fact a breakpoint has been placed is indicated with a dark red background and a dark red bullet at the beginning of the line (see Figure 14-12).

Memory Inspection

Whenever your program is suspended (from a breakpoint, stepping, and so on), you can inspect the memory that is available to your program and explore the values of individual variables.

To facilitate memory inspection, Visual Studio shows the Autos, Locals, and Watch panes at the bottom of its window. If those panes are not there, you can display them using the Debug ➤ Windows menu.

While the Autos and Locals panes automatically select the variables to display, the Watch pane is populated manually according to what you want to see. You can enter a particular variable’s name in the pane, or you can right-click the variable in the code and select Add Watch from the context menu (see Figure 14-13).

The current value of the selected variable appears in the Watch window (see Figure 14-14).

What Is It?

Up to now, you have always had to write a program with several statements and then launch it to see it in action. The interactive mode allows you to enter individual C# statements and run them immediately. You can explore some C# features much faster this way.

How to Launch It?

You can start the interactive mode by selecting View ➤ Other Windows ➤ C# Interactive (see Figure 14-15). You do not even need to have a project created/opened.

Figure 14-16 shows an example interactive session—I have declared a numeric variable, augmented it by ten, and displayed its value.

Notes