Article
11/18/2011

Contract.ForAll Method (Int32, Int32, Predicate<Int32>)

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

Namespace: System.Diagnostics.Contracts
Assembly: mscorlib (in mscorlib.dll)

Syntax

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

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

Parameters

fromInclusive
Type: System.Int32
The first integer to pass to predicate.

toExclusive
Type: System.Int32
One more than the last integer to pass to predicate.

predicate
Type: System.Predicate<Int32>
The function to evaluate for the existence of the integers in the specified range.

Return Value

Type: System.Boolean
true if predicate returns true for all integers starting from fromInclusive to toExclusive - 1.

Exceptions

Exception	Condition
ArgumentNullException	predicate is nulla null reference (Nothing in Visual Basic).
ArgumentException	toExclusive is less than fromInclusive.

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.

Examples

The following example demonstrates how to use the ForAll method to determine whether an array 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

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;
            }
        }
    }
}

Version Information

Silverlight

Supported in: 5, 4

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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