原始碼

path = Server.MapPath("~/TemporaryFile/");
if (false == System.IO.Directory.Exists(path))
{
    System.IO.Directory.CreateDirectory(path);
}
filename = DateTime.Now.ToString("yyyy-MM-dd-HH-mm-ss") + ".xlsx";
path = path + filename;
FileStream fileStream2 = new FileStream(path, FileMode.Create, FileAccess.ReadWrite);
//寫入檔案流
package.SaveAs(fileStream2);
package.Dispose();
 

原因

package.SaveAs(fileStream2);  這句程式碼會FileStream流與該檔案連結，因此被佔用。

解決方法

把FileStream關閉即可   fileStream2.close();