IComparable(Of T) Interface
Defines a generalized comparison method that a value type or class implements to create a type-specific comparison method for ordering instances.
Assembly: mscorlib (in mscorlib.dll)
- In T
The type of objects to compare.
This type parameter is contravariant. That is, you can use either the type you specified or any type that is less derived. For more information about covariance and contravariance, see 2678dc63-c7f9-4590-9ddc-0a4df684d42e.
Thetype exposes the following members.
This interface is implemented by types whose values can be ordered; for example, the numeric and string classes. A value type or class implements the CompareTo method to create a type-specific comparison method suitable for purposes such as sorting.
The interface defines the CompareTo method, which determines the sort order of instances of the implementing type. The IEquatable(Of T) interface defines the Equals method, which determines the equality of instances of the implementing type.
The interface 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 sorting methods such as the List(Of T).Sort method.Notes to Implementers
Replace the type parameter of the interface with the type that is implementing this interface.
The following code example illustrates the implementation of IComparable for a simple Temperature object.
Public Class Address : Implements IComparable(Of Address) Private addr1, addr2, cty, st, coun, postal As String Public Sub New(address1 As String, address2 As String, city As String, _ state As String, postal As String, country As String) Me.addr1 = address1 Me.addr2 = address2 Me.cty = city Me.st = state Me.coun = country Me.postal = postalCode End Sub Public Property Address1 As String Get Return Me.addr1 End Get Set Me.addr1 = value End Set End Property Public Property Address2 As String Get Return Me.addr2 End Get Set Me.addr2 = value End Set End Property Public Property City As String Get Return Me.cty End Get Set Me.cty = value End Set End Property Public Property State As String Get Return Me.st End Get Set Me.st = value End Set End Property Public Property Country As String Get Return Me.coun End Get Set Me.coun = value End Set End Property Public Property PostalCode As String Get Return Me.postal End Get Set Me.postal = value End Set End Property Public Overrides Function ToString() As String Return addr1 & vbCrLf & CStr(IIf(Not String.IsNullOrEmpty(addr2), addr2 & vbCrLf, "")) _ & cty & ", " & st & " " & postal & " " & coun End Function Public Function CompareTo(other As Address) As Integer _ Implements IComparable(Of Address).CompareTo ' If other is Nothing, this instance is greater. If other Is Nothing Then Return 1 Dim otherAddress As String = other.Country & other.State & other.PostalCode & _ other.City & other.Address1 & other.Address2 Return (coun & st & postal & cty & addr1 & addr2).CompareTo(otherAddress) End Function End Class Module Example Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock) Dim addresses As New List(Of Address) addresses.Add(New Address("106 East 5th St.", "", "New City", "MI", "48002", "USA")) addresses.Add(New Address("47 East End Rd.", "", "Huxenplux", "NJ", "20203", "USA")) addresses.Add(New Address("12043 N.E. 72nd St.", "", "Belleville", "WA", "98101", "USA")) addresses.Sort() For Each address As Address In addresses outputBlock.Text &= address.ToString() & vbCrLf & vbCrLf Next End Sub End Module
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