I am trying to add meta data for an image of page.

with this, never write the html code... but if i check !="<a string here>" it work for condition but not the data bind in html code
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{%if (dataRow["MenuItemTeaserImage"].ToString() != ""){return "<meta property=\"og:image\" content=\"http://"+ Domain +"/cms/getattachment/"+ dataRow["MenuItemTeaserImage"].ToString() +"/"+ "\" />"}%}
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I read the guide for K#, method and parameters.... however, it confused me that when to use method and when to use parameters way to do... or they can use together??

Anyone have idea, please share with me. Thank you very much!!