C#条件使用块语句 [英] C# conditional using block statement

问题描述

我有以下代码，但是很尴尬.我如何更好地构建它?我必须让我的消费类实现IDisposable并有条件地构造网络访问类并在完成后处置它吗?

I have the follow code but it is awkward. How could I better structure it? Do I have to make my consuming class implement IDisposable and conditionally construct the network access class and dispose it when I am done?

    protected void ValidateExportDirectoryExists()
    {
        if (useNetworkAccess)
        {
            using (new Core.NetworkAccess(username, password, domain))
            {
                CheckExportDirectoryExists();
            }
        }
        else
        {
            CheckExportDirectoryExists();
        }
    }

推荐答案

基于C#编译器调用Dispose

One option, which is somewhat nasty but would work, based on the fact that the C# compiler calls Dispose only if the resource is non-null:

protected void ValidateExportDirectoryExists()
{
    using (useNetworkAccess 
               ? new Core.NetworkAccess(username, password, domain)
               : null)
    {
        CheckExportDirectoryExists();
    }
}

另一种选择是编写一个静态方法，该方法返回null或NetworkAccess:

Another alternative would be to write a static method which returned either null or a NetworkAccess:

private Core.NetworkAccess CreateNetworkAccessIfNecessary()
{
    return useNetworkAccess
        ? new Core.NetworkAccess(username, password, domain)) : null;
}

然后:

protected void ValidateExportDirectoryExists()
{
    using (CreateNetworkAccessIfNecessary())
    {
        CheckExportDirectoryExists();
    }
}

再次，我仍然不确定我是否不喜欢原始图案……这实际上取决于您需要这种模式的频率.

Again, I'm still not sure I don't prefer the original... it really depends on how often you need this pattern.

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