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.
Assembly: mscorlib (in mscorlib.dll)
- Type: T
An object to compare with this instance.
Return ValueType: System.Int32
A value that indicates the relative order of the objects being compared. The return value has these meanings:
Less than zero
This instance precedes other in the sort order.
This instance occurs in the same position in the sort order as other.
Greater than zero
This instance follows other in the sort order.
provides a strongly typed comparison method for ordering members of a generic collection object. Because of this, it is usually not called directly from developer code. Instead, it is called automatically by methods such as List(T).Sort() and Add.
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 Values section ("precedes", "occurs in the same position as", and "follows) depends on the particular implementation.
By definition, any object compares greater than a null reference (Nothing in Visual Basic), and two null references compare equal to each other.Notes to Implementers
For objects A, B, and C, the following must be true:
A.CompareTo(A) is required to return zero.
If A.CompareTo(B) returns zero, then B.CompareTo(A) is required to return zero.
If A.CompareTo(B) returns zero and B.CompareTo(C) returns zero, then A.CompareTo(C) is required to return zero.
If A.CompareTo(B) returns a value other than zero, then B.CompareTo(A) is required to return a value of the opposite sign.
If A.CompareTo(B) returns a value x that is not equal to zero, and B.CompareTo(C) returns a value y of the same sign as x, then A.CompareTo(C) is required to return a value of the same sign as x and y.Notes to Callers
Use the method to determine the ordering of instances of a class.
The following code example illustrates the implementation of IComparable for a simple Temperature object. The example creates a SortedList(TKey, TValue) collection of strings with Temperature object keys, and adds several pairs of temperatures and strings to the list out of sequence. In the call to the Add method, the SortedList(TKey, TValue) collection uses the IComparable(T) implementation to sort the list entries, which are then displayed in order of increasing temperature.