Just try with following things,
There's a few things you can't access directly it the Orchestration designer, like Generics and Typed Arrays.
If you need string.Split, you'll have to use a helper class.
In a helper class add method like,
public static string GetSourceDate(string receiverGSSegment)
{
string srcDate = string.Empty;
if (!String.IsNullOrEmpty(receiverGSSegment))
{
srcDate = receiverGSSegment.Split('*').ToArray()[4].Substring(0, 4) + '-' + receiverGSSegment.Split('*').ToArray()[4].Substring(4, 2) + '-' + receiverGSSegment.Split('*').ToArray()[4].Substring(6, 2);
}
return srcDate;
}
And use it in Orchestration shape like,