问题
It may be a silly question, but since I can't give it an answer by my own, I will ask it here.
Let we have a module that we want to use in an http handler (the web app is written in C# using ASP.NET) and let that this module implements the IDisposable interface. Then a common approach is to
use the module as below:
using(var module = new ModuleName(param1, param2, param3))
{
}
Is it better to place any code to variables that we are going to use only inside the body of this using statement or before this. In terms of code:
Is it better (and why) the first approach or the second approach:
first approach
using(var module = new ModuleName(param1, param2, param3))
{
int a = Request.GetParam<int>("aNumber");
string b = Request.GetParam<string>("bString");
// and other parameters contained to the http request
}
second approach
int a = Request.GetParam<int>("aNumber");
string b = Request.GetParam<string>("bString");
// and other parameters contained to the http request
using(var module = new ModuleName(param1, param2, param3))
{
}
If there isn't any technical reason -and it is an opinion based decision- that we should prefer the first approach to second approach or vice versa, please let me know, in order to delete my post.
回答1:
It depends on if you need those variables outside of the scope of the using-statement. If so, you need to declare them outside anyway. If not, declare them in the using.
Why? It's all about readability, fail-safety and refactoring.
This is true not only for the using but scopes and variable declaration in general. Read:
- https://codereview.stackexchange.com/questions/6283/variable-declaration-closer-to-usage-vs-declaring-at-the-top-of-method
- https://softwareengineering.stackexchange.com/questions/56585/where-do-you-declare-variables-the-top-of-a-method-or-when-you-need-them
来源：https://stackoverflow.com/questions/25076965/using-statement-best-practice