如何正确清理Excel互操作对象？

问题描述

我在C＃（ ApplicationClass ）中使用Excel interop，并将以下代码放在我的finally子句中：

$ b $ while（System.Runtime.InteropServices.Marshal.ReleaseComObject（excelSheet）！= 0）{}
excelSheet = null; b

  
 GC.Collect（）; 
 GC.WaitForPendingFinalizers（）; 
  

尽管这种作品， Excel.exe 进程仍然处于后台，即使我关闭了Excel。一旦我的应用程序被手动关闭，它才被释放。

我做错了什么，还是有一个替代方法来确保interop对象被妥善处理？

解决方案

Excel不会退出，因为您的应用程序仍然持有对COM对象的引用。

我想你正在调用一个COM对象的至少一个成员，而不分配给变量。

对我来说，这是 excelApp.Worksheets 我直接使用的对象，而不将其分配给变量：

  Worksheet sheet = excelApp。 Worksheets.Open（...）; 
 ... 
 Marshal.ReleaseComObject（sheet）; 
  

我不知道内部的C＃为工作表创建了一个包装器COM对象没有被我的代码释放（因为我没有意识到），并且是为什么没有卸载Excel的原因。

我找到了解决方案关于我在上的问题，这也是C＃中使用COM对象的一个​​很好的规则：

---

所以用这个知识，正确的方法是：

 工作表sheet = excelApp.Worksheets; //<  - 重要的部分
工作表sheet = sheets.Open（...）; 
 ... 
 Marshal.ReleaseComObject（sheets）; 
 Marshal.ReleaseComObject（sheet）; 
  

I'm using the Excel interop in C# (ApplicationClass) and have placed the following code in my finally clause:

while (System.Runtime.InteropServices.Marshal.ReleaseComObject(excelSheet) != 0) { }
excelSheet = null;
GC.Collect();
GC.WaitForPendingFinalizers();

Although this kind of works, the Excel.exe process is still in the background even after I close Excel. It is only released once my application is manually closed.

What am I doing wrong, or is there an alternative to ensure interop objects are properly disposed of?

解决方案

Excel does not quit because your application is still holding references to COM objects.

I guess you're invoking at least one member of a COM object without assigning it to a variable.

For me it was the excelApp.Worksheets object which I directly used without assigning it to a variable:

Worksheet sheet = excelApp.Worksheets.Open(...);
...
Marshal.ReleaseComObject(sheet);

I didn't know that internally C# created a wrapper for the Worksheets COM object which didn't get released by my code (because I wasn't aware of it) and was the cause why Excel was not unloaded.

I found the solution to my problem on this page, which also has a nice rule for the usage of COM objects in C#:

---

So with this knowledge the right way of doing the above is:

Worksheets sheets = excelApp.Worksheets; // <-- The important part
Worksheet sheet = sheets.Open(...);
...
Marshal.ReleaseComObject(sheets);
Marshal.ReleaseComObject(sheet);

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