من خودم همیشه از این روش استفاده میکنم و جواب هم میده
static void excelsave()
{
try
{
Application app = new Application();
string execPath =
Path.GetDirectoryName(Assembly.GetExecutingAssembly().CodeBase);
Workbook book = app.Workbooks.Open(@"c:\test.xls");
Worksheet sheet = (Worksheet)book.Worksheets[1];
Range range = sheet.get_Range("A1");
range.Columns.ColumnWidth = 22.34;
range = sheet.get_Range("B1");
range.Columns.ColumnWidth = 22.34;
sheet.get_Range("A1", "B1").Font.Bold = true;
book.SaveAs(@"c:\test2.xls"); // or book.Save();
book.Close();
}
catch (Exception ex)
{
}
}