Predicate Generic Delegate
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Delegate Function Predicate(Of T) ( _ obj As T _ ) As Boolean 'Usage Dim instance As New Predicate(Of T)(AddressOf HandlerMethod)
J# supports the use of generic types and methods, but not the declaration of new ones.
JScript does not support generic types and methods.
Type Parameters
- T
The type of the object to compare.
Parameters
- obj
The object to compare against the criteria defined within the method represented by this delegate.
Return Value
true if obj meets the criteria defined within the method represented by this delegate; otherwise, false.The following code example uses a Predicate delegate with the Array.Find method to search an array of Point structures. The method the delegate represents, ProductGT10, returns true if the product of the X and Y fields is greater than 100,000. The Find method calls the delegate for each element of the array, stopping at the first point that meets the test condition.
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| Visual Basic and C# users do not need to create the delegate explicitly, or to specify the type argument of the generic method. The compilers determine the necessary types from the method arguments you supply. |
Imports System Imports System.Drawing Public Class Example Public Shared Sub Main() ' Create an array of five Point structures. Dim points() As Point = { new Point(100, 200), _ new Point(150, 250), new Point(250, 375), _ new Point(275, 395), new Point(295, 450) } ' To find the first Point structure for which X times Y ' is greater than 100000, pass the array and a delegate ' that represents the ProductGT10 method to the Shared ' Find method of the Array class. Dim first As Point = Array.Find(points, _ AddressOf ProductGT10) ' Note that you do not need to create the delegate ' explicitly, or to specify the type parameter of the ' generic method, because the compiler has enough ' context to determine that information for you. ' Display the first structure found. Console.WriteLine("Found: X = {0}, Y = {1}", _ first.X, first.Y) End Sub ' This method implements the test condition for the Find ' method. Private Shared Function ProductGT10(ByVal p As Point) As Boolean If p.X * p.Y > 100000 Then Return True Else Return False End If End Function End Class ' This code example produces the following output: ' 'Found: X = 275, Y = 395
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The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
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