public static DbUnit Subtract(DbUnit a, DbUnit b) { if (a.ValueType == b.ValueType) { return(a.subtract(b)); } else { return(null); } }
public static DbUnit Add(DbUnit a, DbUnit b) { if (a.ValueType == b.ValueType) { return(a.add(b)); } else { return(null); } }
protected abstract DbUnit subtract(DbUnit b);
protected abstract DbUnit add(DbUnit b);