Array.TrueForAll<T> Method

Determines whether every element in the array matches the conditions defined by the specified predicate.

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

public static bool TrueForAll<T>(
	T[] array,
	Predicate<T> match
)

Type Parameters

T

The type of the elements of the array.

Parameters

array
Type: T[]

The one-dimensional, zero-based Array to check against the conditions.

match
Type: System.Predicate<T>

The predicate that defines the conditions to check against the elements.

Return Value

Type: System.Boolean
true if every element in array matches the conditions defined by the specified predicate; otherwise, false. If there are no elements in the array, the return value is true.

ExceptionCondition
ArgumentNullException

array is null.

-or-

match is null.

The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of array are individually passed to the Predicate<T>, and processing is stopped when the delegate returns false for any element.

This method is an O(n) operation, where n is the Length of array.

The following example determines whether the last character of each element in a string array is a number. It creates two string arrays. The first array includes both strings that end with alphabetic characters and strings that end with numeric characters. The second array consists only of strings that end with numeric characters. The example also defines an EndWithANumber method whose signature matches the Predicate<T> delegate. The example passes each array to the TrueForAll<T> method along with a delegate that represents the EndsWithANumber method.

using System;

public class Example
{
   public static void Main()
   {
      String[] values1 = { "Y2K", "A2000", "DC2A6", "MMXIV", "0C3" };
      String[] values2 = { "Y2", "A2000", "DC2A6", "MMXIV_0", "0C3" };


      if (Array.TrueForAll(values1, EndsWithANumber))
         Console.WriteLine("All elements end with an integer.");
      else
         Console.WriteLine("Not all elements end with an integer.");

      if (Array.TrueForAll(values2, EndsWithANumber))
         Console.WriteLine("All elements end with an integer.");
      else
         Console.WriteLine("Not all elements end with an integer.");
   }

   private static bool EndsWithANumber(String value) 
   {
      int s;
      return Int32.TryParse(value.Substring(value.Length - 1), out s);
   }
}
// The example displays the following output: 
//       Not all elements end with an integer. 
//       All elements end with an integer.

The following example is similar to the first, except that it passes the string array to the TrueForAll<T> method along with a lambda expression that determines whether a particular array element ends with the string representation of a number.

using System;

public class Example
{
   public static void Main()
   {
      String[] values = { "Y2K", "A2000", "DC2A6", "MMXIV", "0C3" };
      if (Array.TrueForAll(values, value => {
                                      int s; 
                                      return Int32.TryParse(value.Substring(value.Length - 1), out s); }
                                   ))
         Console.WriteLine("All elements end with an integer.");
      else
         Console.WriteLine("Not all elements end with an integer.");
   }
}
// The example displays the following output: 
//        Not all elements end with an integer.

In both cases, the TrueForAll<T> method returns false as soon as it encounters the first array element that does not end in a number. Otherwise, it returns true after iterating all the elements in the array.

NoteNote

As both examples show, in C# and Visual Basic, it is not necessary to create the Predicate<string> delegate (Predicate(Of String) in Visual Basic) explicitly. These languages infer the correct delegate from context and create it automatically.

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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