Contract.ForAll(Of T) Method (IEnumerable(Of T), Predicate(Of T))
.NET Framework (current version)
Determines whether all the elements in a collection exist within a function.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function ForAll(Of T) ( collection As IEnumerable(Of T), predicate As Predicate(Of T) ) As Boolean
Parameters
- collection
-
Type:
System.Collections.Generic.IEnumerable(Of T)
The collection from which elements of type T will be drawn to pass to predicate.
- predicate
-
Type:
System.Predicate(Of T)
The function to evaluate for the existence of all the elements in collection.
Return Value
Type: System.Booleantrue if and only if predicate returns true for all elements of type T in collection.
Type Parameters
- T
The type that is contained in collection.
| Exception | Condition |
|---|---|
| ArgumentNullException | collection or predicate is null. |
The following example demonstrates how to use the ForAll(Of T) method to determine whether a collection has a null element.
Imports System Imports System.Diagnostics.Contracts Imports System.Collections.Generic Class Program ' Start application with at least two arguments. Shared Sub Main(ByVal args() As String) args(1) = Nothing Contract.Requires(Not (args Is Nothing) AndAlso Contract.ForAll(args, Function(s) s Is Nothing)) ' test the ForAll method. This is only for purpose of demonstrating how ForAll works. CheckIndexes(args) Dim numbers As New Stack(Of String) numbers.Push("one") numbers.Push("two") numbers.Push("three") numbers.Push("four") numbers.Push("five") Contract.Requires(Not (numbers Is Nothing) AndAlso Not Contract.ForAll(numbers, Function(s) s Is Nothing)) ' test the ForAll generic overload. This is only for purpose of demonstrating how ForAll works. CheckTypeArray(numbers) End Sub 'Main Private Shared Function CheckIndexes(ByVal args() As String) As Boolean Try If Not (args Is Nothing) AndAlso Not Contract.ForAll(0, args.Length, Function(i) args(i) Is Nothing) Then Throw New ArgumentException("The parameter array has a null element", "args") End If Return True Catch e As ArgumentException Console.WriteLine(e.Message) Return False End Try End Function 'CheckIndexes Private Shared Function CheckTypeArray(ByVal xs As Stack(Of String)) As Boolean Try If Not (xs Is Nothing) AndAlso Not Contract.ForAll(xs, Function(s) s Is Nothing) Then Throw New ArgumentException("The parameter array has a null element", "Stack") End If Return True Catch e As ArgumentException Console.WriteLine(e.Message) Return False End Try End Function 'CheckTypeArray End Class 'Program
Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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