Zaphod Zaphod - 3 months ago 45
C# Question

Cannot close Excel.exe after Interop process

I'm having an issue with Excel Interop.

The Excel.exe doesn't close even if when I realease instances.

Here is my code :

using xl = Microsoft.Office.Interop.Excel;


xl.Application excel = new xl.Application();
excel.Visible = true;
excel.ScreenUpdating = false;
if (wordFile.Contains(".csv") || wordFile.Contains(".xls"))
{
//typeExcel become a string of the document name
string typeExcel = wordFile.ToString();
xl.Workbook workbook = excel.Workbooks.Open(typeExcel,
oMissing, oMissing, oMissing, oMissing,
oMissing, oMissing, oMissing, oMissing,
oMissing, oMissing, oMissing, oMissing,
oMissing, oMissing);
object outputFileName = null;
if (wordFile.Contains(".xls"))
{
outputFileName = wordFile.Replace(".xls", ".pdf");
}
else if (wordFile.Contains(".csv"))
{
outputFileName = wordFile.Replace(".csv", ".pdf");
}

workbook.ExportAsFixedFormat(XlFixedFormatType.xlTypePDF, outputFileName,
XlFixedFormatQuality.xlQualityStandard, oMissing,
oMissing, oMissing, oMissing, oMissing, oMissing);

object saveChanges = xl.XlSaveAction.xlDoNotSaveChanges;
((xl._Workbook)workbook).Close(saveChanges, oMissing, oMissing);

Marshal.ReleaseComObject(workbook);
workbook = null;
}


I saw that, with the
Marshal.RealeaseComObject
it should be work, but nothing.
How can I fix this?

Thank you.

Answer

Simple rule: avoid using double-dot-calling expressions, such as this:

var workbook = excel.Workbooks.Open(/*params*/)

...because in this way you create RCW objects not only for workbook, but for Workbooks, and you should release it too (which is not possible if a reference to the object is not maintained).

So, the right way will be:

var workbooks = excel.Workbooks;
var workbook = workbooks.Open(/*params*/)

//business logic here

Marshal.ReleaseComObject(workbook);
Marshal.ReleaseComObject(workbooks);
Marshal.ReleaseComObject(excel);
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