Contract.ForAll Method

Definition

Namespace:

System.Diagnostics.Contracts

Assembly:

System.Diagnostics.Contracts.dll

Overloads

ForAll(Int32, Int32, Predicate<Int32>)	Determines whether a particular condition is valid for all integers in a specified range.
ForAll<T>(IEnumerable<T>, Predicate<T>)	Determines whether all the elements in a collection exist within a function.

ForAll(Int32, Int32, Predicate<Int32>)

Source:

Contracts.cs

Determines whether a particular condition is valid for all integers in a specified range.

public:
 static bool ForAll(int fromInclusive, int toExclusive, Predicate<int> ^ predicate);

public static bool ForAll (int fromInclusive, int toExclusive, Predicate<int> predicate);

static member ForAll : int * int * Predicate<int> -> bool

Public Shared Function ForAll (fromInclusive As Integer, toExclusive As Integer, predicate As Predicate(Of Integer)) As Boolean

Parameters

fromInclusive

Int32

The first integer to pass to predicate.

toExclusive

Int32

One more than the last integer to pass to predicate.

predicate

Predicate<Int32>

The function to evaluate for the existence of the integers in the specified range.

Returns

Boolean

true if predicate returns true for all integers starting from fromInclusive to toExclusive - 1.

Exceptions

ArgumentNullException

predicate is null.

ArgumentException

toExclusive is less than fromInclusive.

Examples

The following example demonstrates how to use the ForAll method to determine whether an array has a null element.

using System;
using System.Diagnostics.Contracts;
using System.Collections.Generic;
namespace AssumeEx
{
    class Program
    {
        // Start application with at least two arguments
        static void Main(string[] args)
        {
            args[1] = null;
            Contract.Requires(args != null && Contract.ForAll(0, args.Length, i => args[i] != null));
            // test the ForAll method.  This is only for purpose of demonstrating how ForAll works.
            CheckIndexes(args);
            Stack<string> numbers = new Stack<string>();
            numbers.Push("one");
            numbers.Push("two");
            numbers.Push(null);
            numbers.Push("four");
            numbers.Push("five");
            Contract.Requires(numbers != null && !Contract.ForAll(numbers, (String x) => x != null));
            // test the ForAll generic overload.  This is only for purpose of demonstrating how ForAll works.
            CheckTypeArray(numbers);
        }

        private static bool CheckIndexes(string[] args)
        {
            try
            {
                if (args != null && !Contract.ForAll(0, args.Length, i => args[i] != null))
                    throw new ArgumentException("The parameter array has a null element", "args");
                return true;
            }
            catch (ArgumentException e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
        }
        private static bool CheckTypeArray(IEnumerable<String> xs)
        {
            try
            {
                if (xs != null && !Contract.ForAll(xs, (String x) => x != null))
                    throw new ArgumentException("The parameter array has a null element", "indexes");
                return true;
            }
            catch (ArgumentException e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
        }
    }
}

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


    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

Remarks

The toExclusive parameter is one more than the last integer to facilitate using the length of a range of integers starting at 0. For example, it would be set to 5 for integers 0 through 4.

See also

• TrueForAll(Predicate<T>)

ForAll<T>(IEnumerable<T>, Predicate<T>)

Source:

Contracts.cs

Determines whether all the elements in a collection exist within a function.

public:
generic <typename T>
 static bool ForAll(System::Collections::Generic::IEnumerable<T> ^ collection, Predicate<T> ^ predicate);

public static bool ForAll<T> (System.Collections.Generic.IEnumerable<T> collection, Predicate<T> predicate);

static member ForAll : seq<'T> * Predicate<'T> -> bool

Public Shared Function ForAll(Of T) (collection As IEnumerable(Of T), predicate As Predicate(Of T)) As Boolean

Type Parameters

T

The type that is contained in collection.

Parameters

collection

IEnumerable<T>

The collection from which elements of type T will be drawn to pass to predicate.

predicate

Predicate<T>

The function to evaluate for the existence of all the elements in collection.

Returns

Boolean

true if and only if predicate returns true for all elements of type T in collection.

Exceptions

ArgumentNullException

collection or predicate is null.

Examples

The following example demonstrates how to use the ForAll method to determine whether a collection has a null element.

using System;
using System.Diagnostics.Contracts;
using System.Collections.Generic;
namespace AssumeEx
{
    class Program
    {
        // Start application with at least two arguments
        static void Main(string[] args)
        {
            args[1] = null;
            Contract.Requires(args != null && Contract.ForAll(0, args.Length, i => args[i] != null));
            // test the ForAll method.  This is only for purpose of demonstrating how ForAll works.
            CheckIndexes(args);
            Stack<string> numbers = new Stack<string>();
            numbers.Push("one");
            numbers.Push("two");
            numbers.Push(null);
            numbers.Push("four");
            numbers.Push("five");
            Contract.Requires(numbers != null && !Contract.ForAll(numbers, (String x) => x != null));
            // test the ForAll generic overload.  This is only for purpose of demonstrating how ForAll works.
            CheckTypeArray(numbers);
        }

        private static bool CheckIndexes(string[] args)
        {
            try
            {
                if (args != null && !Contract.ForAll(0, args.Length, i => args[i] != null))
                    throw new ArgumentException("The parameter array has a null element", "args");
                return true;
            }
            catch (ArgumentException e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
        }
        private static bool CheckTypeArray(IEnumerable<String> xs)
        {
            try
            {
                if (xs != null && !Contract.ForAll(xs, (String x) => x != null))
                    throw new ArgumentException("The parameter array has a null element", "indexes");
                return true;
            }
            catch (ArgumentException e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
        }
    }
}

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


    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

See also

• TrueForAll(Predicate<T>)