T-SQL (varchar (máximo) vs CLR (cadena, SqlString, SqlChars)?

Lo que debe hacer es agregar el atributo SqlFacet (MaxSize =-1) al parámetro:

[return: SqlFacet(MaxSize = -1)]
[Microsoft.SqlServer.Server.SqlFunction(IsDeterministic = true)]
public static SqlString YourSqlFunction([SqlFacet(MaxSize = -1)]SqlString sourceSS)
{ return new }