Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.
A value that indicates the relative order of the objects being compared. The return value has these meanings:
Less than zero
This instance precedes obj in the sort order.
This instance occurs in the same position in the sort order as obj.
Greater than zero
This instance follows obj in the sort order.
The IComparable.CompareTo(object) method is implemented by types whose values can be ordered or sorted. It is called automatically by methods of non-generic collection objects, such as Array.Sort(Array), to order each member of the array. If a custom class or structure does not implement IComparable, its members cannot be ordered and the sort operation can throw an InvalidOperationException.
This method is only a definition and must be implemented by a specific class or value type to have effect. The meaning of the comparisons specified in the Return Value section ("precedes", "occurs in the same position as", and "follows") depends on the particular implementation.
By definition, any object compares greater than (or follows) null, and two null references compare equal to each other.
The parameter, obj, must be the same type as the class or value type that implements this interface; otherwise, an ArgumentException is thrown.