Visual Studio Hacks

Refactor Your Code #14

Chapter 2, Master the Editor

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67

HACK

interface IStart

{

bool IsStarted { get; set; }

}

Visual Studio will also modify the existing class to implement the new inter-

face. The Extract Interface function is a great time-saver when you need to

create an interface that is based on a current class.

Parameter Functions

The next three functions on the menu all focus on working with parame-

ters. Since the sample class does not currently contain any methods with

parameters, go ahead and add a new method with a number of different

parameters. Here is a method called

Collision that you can add to this class:

public void Collision(DateTime CrashDate, int Speed, int DamagePct)

{

int costMultiplier = 1;

// Do stuff

}

As you can see, this method has a local variable called costMultiplier and

sets the value to

1. But suppose that costMultiplier varies from vehicle to

vehicle. In this case, you’d want to pass in this multiplier as a parameter

instead of creating it as a local variable. The first of the parameter refactor-

ing functions will do just that. First, right-click on the

costMultiplier vari-

able and select the Promote Local Variable to Parameter function. This will

take the local variable and add it as a parameter to the method. Here is a

look at the modified code:

public void Collision(int costMultiplier, DateTime CrashDate,

int Speed, int DamagePct)

{

// Do stuff

}

You may be thinking that this is not a big deal; it is basically cut and paste.

But Visual Studio also goes and looks for any calls to this method and modi-

fies them as well. If you were calling this method before with the following

line of code:

Collision(DateTime.Now, 60, 10);

this method call would be changed to the following:

Collision(1, DateTime.Now, 60, 10);

Notice that Visual Studio not only adds the new parameter, but also passes

in the value that the local variable was set to as well, saving time and ensur-

ing that existing code continues to work as it did before.

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Chapter 2, Master the Editor

#14 Refactor Your Code

HACK

Suppose you decide that you don’t need the CrashDate parameter. If you

won’t be using it in the method, you can remove this parameter using the

second of these parameter refactoring functions, called Remove Parameters.

First, right-click on the method name and click Remove Parameters in the

Refactor menu. You’ll be shown the Remove Parameters dialog, which is

shown in Figure 2-37.

In the Remove Parameters dialog, you can select the

CrashDate parameter,

click Remove, and then click OK. You are then shown a Preview Changes

dialog showing the changes that will be made to any calls to this method.

After clicking Apply on that screen, those changes will be made. Any calls to

this method will have this parameter removed, and the parameter will be

removed from the method signature.

Further, suppose you decide that you don’t want

costMultiplier to be the

first parameter, but rather the last parameter. This is where the last of the

parameter functions comes in. First, right-click on the method, then choose

the Reorder Parameters menu item on the Refactor menu. This will display

the Reorder Parameters dialog, which is shown in Figure 2-38.

Figure 2-37. Remove Parameters dialog