C# 自动生成 Excel
...
Excel.Application oXL;
Excel._Workbook oWB;
Excel._Worksheet oSheet;
oXL = new Excel.Application();
oWB = (Excel._Workbook)oXL.ActiveWorkbook;
oSheet = (Excel._Worksheet)oWB.Sheets[1];
oSheet.Cells[5,10] = "Value";
...
在崩溃时产生这个：
Unhandled Exception: System.NullReferenceException: Object reference not set to
an instance of an object.
at ConsoleApplication1.Program.Main(String[] args) in C:\Wherever\Visual Studio 2008\Projects\ConsoleApplication20\ConsoleApplication20\Program.
cs:line 60
在这种情况下，第 60 行是
oSheet = (Excel._Worksheet)oWB.Sheets[1];
如果写入该行，也会发生同样的事情
oSheet = (Excel._Worksheet)oWB.ActiveSheet;。
此时 Excel 已在屏幕上打开，并带有新的工作表。
...
Excel.Application oXL;
Excel._Workbook oWB;
Excel._Worksheet oSheet;
oXL = new Excel.Application();
oWB = (Excel._Workbook)oXL.ActiveWorkbook;
oSheet = (Excel._Worksheet)oWB.Sheets[1];
oSheet.Cells[5,10] = "Value";
...
yields this at crash:
Unhandled Exception: System.NullReferenceException: Object reference not set to
an instance of an object.
at ConsoleApplication1.Program.Main(String[] args) in C:\Wherever\Visual Studio 2008\Projects\ConsoleApplication20\ConsoleApplication20\Program.
cs:line 60
In this case, line 60 is
oSheet = (Excel._Worksheet)oWB.Sheets[1];
and the same thing happens if the line is written
oSheet = (Excel._Worksheet)oWB.ActiveSheet;.
Excel is already open onscreen at the time, with a fresh worksheet in place.
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该错误告诉您 oWB 为空。它为空，因为与从 GUI 打开 Excel 不同，自动化不会创建新的 3 页书。您需要先专门加载一本书，或者添加一本书。
请参阅此处的示例http://support.microsoft.com/kb/302084，其中显式添加了可以使用的新工作簿
The error is telling you that oWB is null. It is null because unlike opening Excel from a GUI, automation does not create a new 3-sheet book. You need to specifically load a book first, or add one.
See example here http://support.microsoft.com/kb/302084 where it explicitly adds a new workbook to play with