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CompareTo Method

[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]

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.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)
Function CompareTo ( _
	obj As Object _
) As Integer
int CompareTo(
	Object obj
)
int CompareTo(
	Object^ obj
)
abstract CompareTo : 
        obj:Object -> int 
function CompareTo(
	obj : Object
) : int

Parameters

obj
Type: System..::..Object
An object to compare with this instance.

Return Value

Type: System..::..Int32
A value that indicates the relative order of the objects being compared. The return value has these meanings:

Value

Meaning

Less than zero

This instance precedes obj in the sort order.

Zero

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 CompareTo 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, 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) nullNothingnullptrunita null reference (Nothing in Visual Basic), 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.

Notes to Implementers

For objects A, B and C, the following must be true:

A.CompareTo(A) must return zero.

If A.CompareTo(B) returns zero, then B.CompareTo(A) must return zero.

If A.CompareTo(B) returns zero and B.CompareTo(C) returns zero, then A.CompareTo(C) must return zero.

If A.CompareTo(B) returns a value other than zero, then B.CompareTo(A) must return a value of the opposite sign.

If A.CompareTo(B) returns a value x not equal to zero, and B.CompareTo(C) returns a value y of the same sign as x, then A.CompareTo(C) must return a value of the same sign as x and y.

Notes to Callers

Use the CompareTo method to determine the ordering of instances of a class.