in TeamCity.ServiceMessages/Write/Special/Impl/Writer/TeamCityBuildStatusWriter.cs [33:39]
public void WriteBuildParameter(string parameterName, string parameterValue)
{
if (parameterName == null) throw new ArgumentNullException(nameof(parameterName));
if (parameterValue == null) throw new ArgumentNullException(nameof(parameterValue));
//##teamcity[setParameter name='ddd' value='fff']
PostMessage(new ServiceMessage("setParameter") {{"name", parameterName}, {"value", parameterValue}});
}