Microsoft 9GD00001 manual Parameter name

362Microsoft Visual Studio 2010: A Beginner’s Guide

could end up saving bad data. Since AddNewCustomer doesn’t have an implementation, this is all speculation, but this outlines a few of the many problems that can occur if you allow your business objects to accept data that is bad for your program.

The macro demonstrated in this section will show how to check a string parameter for null, empty, or white space and throw an ArgumentNullException. This will prevent callers from passing bad data and give them a meaningful message. To create a macro, you will need to locate the position in the code where the macro starts (if applicable), start recording, perform VS actions, and stop recording. It’s somewhat like using a video recorder where you have to find a TV show, start the recording, allow the show to play, and then stop recording. Perform the following steps to create the parameter validation macro:

1.Click the firstName parameter of the AddNewCustomer method so that the cursor is inside of the firstName parameter identifier. This is important because we need the parameter name in the code.

2.Start the macro recorder by selecting Tools Macros Record TemporaryMacro or press

CTRL-SHIFT-R.

3.For C#, press CTRL-LEFT ARROW, CTRL-SHIFT-RIGHT ARROW, and CTRL-C. For VB, press

CTRL-LEFT ARROW, CTRL-SHIFT-RIGHT ARROW, SHIFT-LEFT ARROW, and CTRL-C. This copies

the parameter name.

4.For C#, press CTRL-Fto bring up the Find And Replace window, type { into Find What, click Find Next, Close the Find And Replace window, press END, and press ENTER. For VB, press END and press ENTER. This positions the cursor to begin entering code.

5.Type if and press TAB twice (the if snippet), type string.IsNullOrWhiteSpace( into the condition, press CTRL-Vto paste the parameter name as the argument, and type ). For C#, press ENTER. For VB, press DOWN ARROW. The cursor moves to the body of the if statement (as you would expect with the if snippet). This sets up the validation check for the parameter, seeing if it is null (Nothing in VB), an empty string, or some white space character such as space or tab.

6.Type throw new ArgumentNullException(", press CTRL-Vto paste the parameter name, type ", ", press CTRL-Vto paste the parameter name, type a space, and type value is not valid."). For C#, add a semicolon, ;, to the end of the line. This is the action to perform when the value is not valid, throwing an exception to let the caller know that the value is not good.

7.Press DOWN ARROW and press ENTER. This positions the cursor after the code, which might be convenient if you want to continue typing from this point.

8.Select Tools Macros Stop Recording TemporaryMacro or press CTRL-SHIFT-Rto stop recording.