这里是(潜在的)问题:
我创建一个COM对象,然后使用'foreach'遍历它返回的集合中的每个元素。我需要释放集合中迭代的每个元素吗? (请参见下面的代码。)如果是这样,我想不出一种有效地从“ finally”语句中释放它的方法,以防万一在操作该项目时出现错误。
有什么建议吗?
private static void doStuff()
{
ComObjectClass manager = null;
try
{
manager = new ComObjectClass();
foreach (ComObject item in manager.GetCollectionOfItems())
{
Log.Debug(item.Name);
releaseComObject(item); // <-- Do I need this line?
// It isn't in a 'finally' block...
// ...Possible memory leak?
}
}
catch (Exception) { }
finally
{
releaseComObject(manager);
}
}
private static void releaseComObject(object instance)
{
if (instance != null)
{
try
{
System.Runtime.InteropServices.Marshal.ReleaseComObject(instance);
}
catch
{
/* log potential memory leak */
Log.Debug("Potential memory leak: Unable to release COM object.");
}
finally
{
instance = null;
}
}
}
您不应将foreach
语句与COM对象一起使用,因为在无法控制释放的幕后进行了引用。我将切换到for
循环,并确保您never use two dots with COM objects.
外观如下:
try
{
manager = new ComObjectClass();
ComObject comObject = null;
ComObject[] collectionOfComItems = manager.GetCollectionOfItems();
try
{
for(int i = 0; i < collectionOfComItems.Count; i++)
{
comObject = collectionOfComItems[i];
ReleaseComObject(comObject);
}
}
finally
{
ReleaseComObject(comObject);
}
}
finally
{
ReleaseComObject(manager);
}
另一种方法是创建自己的迭代器函数:
IEnumerable<ComObject> GetChildItems(this ComObjectClass manager) {
ComObject comObject = null;
ComObject[] collectionOfComItems = manager.GetCollectionOfItems();
for (int i = 0; i < collectionOfComItems.Length; i++) {
try {
comObject = collectionOfComItems[i];
yield return comObject;
} finally {
if (comObject != null)
Marshal.ReleaseComObject(comObject);
}
}
yield break;
}
private static void doStuff() {
ComObjectClass manager = null;
try {
manager = new ComObjectClass();
foreach (ComObject item in manager.GetChildItems()) {
Log.Debug(item.Name);
}
} finally {
releaseComObject(manager);
}
}
我认为这使您的代码更具可读性,尤其是当您需要多次遍历子项时。