程式碼

CT_Hdr header = new CT_Hdr();
	var hP = header.AddNewP();
	hP.pPr = new CT_PPr { 
		spacing = new CT_Spacing { after = 20, line = "360", lineRule = ST_LineSpacingRule.auto },
		jc = new CT_Jc { val = ST_Jc.center },
		rPr = new CT_ParaRPr {
			b = new CT_OnOff { val = true },
			rFonts = new CT_Fonts { eastAsia = "標楷體"},
			sz = new  CT_HpsMeasure { val = 34 } ,
			szCs = new  CT_HpsMeasure { val = 34 }
			}
		};
	var hpr = hP.AddNewR();
	hpr.rPr = new CT_RPr { 
		b = new CT_OnOff { val = true }, 
		rFonts = new CT_Fonts { eastAsia = "標楷體" },
		sz = new CT_HpsMeasure { val = 34 }, 
		szCs = new CT_HpsMeasure { val = 34}
	};

	hpr.AddNewT().Value = "This is header";

	XWPFDocument doc = new XWPFDocument();

	var document = doc.Document;



	var body = document.body;
	if (!body.IsSetSectPr())
	{
		body.sectPr = new NPOI.OpenXmlFormats.Wordprocessing.CT_SectPr();
	}
	var section = body.sectPr;

	var myHeader = doc.CreateRelationship(XWPFRelation.HEADER, XWPFFactory.GetInstance(), doc.HeaderList.Count + 1) as XWPFHeader;
	myHeader.SetHeaderFooter(header);
	CT_HdrFtrRef myHeaderRef = section.AddNewHeaderReference();

	myHeaderRef.type = ST_HdrFtr.@default;

	myHeaderRef.id = myHeader.GetPackageRelationship().Id;

	using (var fileStream = new FileStream(@"{PATH}", FileMode.Create))
	{
		doc.Write(fileStream);

	}

 重點回顧

1. 宣告一個CT_Hdr 物件
2. XWPFDocument 呼叫 CreateRelationship方法，接著設定Header

   var myHeader = doc.CreateRelationship(XWPFRelation.HEADER, XWPFFactory.GetInstance(), doc.HeaderList.Count + 1) as XWPFHeader; 
   myHeader.SetHeaderFooter(header);

3. 在Section設定Header參考

   var section = body.sectPr;
   CT_HdrFtrRef myHeaderRef = section.AddNewHeaderReference();
   
   myHeaderRef.type = ST_HdrFtr.@default;
   
   myHeaderRef.id = myHeader.GetPackageRelationship().Id;

 結果截圖