MainDocumentPart mainPart = doc.MainDocumentPart;
List<sdtblock> sdtList = mainPart.Document.Descendants<sdtblock>().ToList();
SdtBlock sdtA = null;
foreach (SdtBlock sdt in sdtList)
{
var test = sdt.SdtProperties.GetFirstChild<tag>().Val.Value;
if (sdt.SdtProperties.GetFirstChild<tag>().Val.Value == replacestring)
{
sdtA = sdt;
break;
}
}
sdtA.AppendChild(table);</tag></tag></sdtblock></sdtblock>