Applies a Tag to a content item. If the tag text does not already exist, it is created. The newly created ID is accessible via the returned TagData. Adds the tag for the current user and the Tag is saved under the current site language. 

This method can be accessed through the Tags.asmx file located in:

~/Workarea/webservices/WebServiceAPI/Community/Tags.asmx

[SoapHeader("AuthHeader")]
[SoapHeader("RequestInfoHeader")]
[WebMethod(MessageName = "AddTagToContent", Description = "Applies a Tag to a piece of content.  If the tag text does not already exist, it is created.  The newly created Id is accessible via the returned TagData. Adds the tag for the current user and the Tag is saved under the current site language.")]
public TagData AddTagToContent(string tagText, long contentId);

<SoapHeader("AuthHeader")>
<SoapHeader("RequestInfoHeader")>
<WebMethod(MessageName = "AddTagToContent", Description = "Applies a Tag to a piece of content.  If the tag text does not already exist, it is created.  The newly created Id is accessible via the returned TagData. Adds the tag for the current user and the Tag is saved under the current site language.")>
Public Function AddTagToContent(tagText As string, contentId As long) As TagData