Array.TrueForAll<T>(T[], Predicate<T>) Method

Reference

Definition

Namespace:: System

Assemblies:: mscorlib.dll, System.Runtime.dll

Assemblies:: netstandard.dll, System.Runtime.dll

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: Array.cs

Source:: Array.cs

Source:: Array.cs

Important

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

public: generic <typename T>  static bool TrueForAll(cli::array <T> ^ array, Predicate<T> ^ match);

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

static member TrueForAll : 'T[] * Predicate<'T> -> bool

Public Shared Function TrueForAll(Of T) (array As T(), match As Predicate(Of T)) As Boolean

Type Parameters

T

The type of the elements of the array.

Parameters

array: T[]

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

match: Predicate<T>

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

Returns

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.

Exceptions

ArgumentNullException

array is null.

-or-

match is null.

Examples

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 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 int.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.

open System  let endsWithANumber (value: string) =     value.Substring(value.Length - 1)     |> Int32.TryParse     |> fst  let values1 = [| "Y2K"; "A2000"; "DC2A6"; "MMXIV"; "0C3" |] let values2 = [| "Y2"; "A2000"; "DC2A6"; "MMXIV_0"; "0C3" |]  if Array.TrueForAll(values1, endsWithANumber) then     printfn "All elements end with an integer." else     printfn "Not all elements end with an integer."  if Array.TrueForAll(values2, endsWithANumber) then     printfn "All elements end with an integer." else     printfn "Not all elements end with an integer."   // The example displays the following output: //       Not all elements end with an integer. //       All elements end with an integer.

Module Example    Public Sub Main()       Dim values1() As String = { "Y2K", "A2000", "DC2A6", "MMXIV", "0C3" }       Dim values2() As String = { "Y2", "A2000", "DC2A6", "MMXIV_0", "0C3" }         If Array.TrueForAll(values1, AddressOf EndsWithANumber) Then          Console.WriteLine("All elements end with an integer.")       Else          Console.WriteLine("Not all elements end with an integer.")       End If                 If Array.TrueForAll(values2, AddressOf EndsWithANumber) Then          Console.WriteLine("All elements end with an integer.")       Else          Console.WriteLine("Not all elements end with an integer.")       End If       End Sub     Private Function EndsWithANumber(value As String) As Boolean       Dim s As Integer       Return Int32.TryParse(value.Substring(value.Length - 1), s)    End Function End Module ' 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 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 int.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.

open System  let values = [| "Y2K"; "A2000"; "DC2A6"; "MMXIV"; "0C3" |] if Array.TrueForAll(values,      fun value ->          value.Substring(value.Length - 1)          |> Int32.TryParse          |> fst) then     printfn "All elements end with an integer." else     printfn "Not all elements end with an integer."         // The example displays the following output: //        Not all elements end with an integer.

Module Example    Public Sub Main()       Dim values() As String = { "Y2K", "A2000", "DC2A6", "MMXIV", "0C3" }       'Dim values2() As String = { "Y2", "A2000", "DC2A6", "MMXIV_0", "0C3" }        If Array.TrueForAll(values, Function(value)                                       Dim s As Integer                                      Return Int32.TryParse(value.Substring(value.Length - 1), s)                                   End Function) Then          Console.WriteLine("All elements end with an integer.")       Else          Console.WriteLine("Not all elements end with an integer.")       End If       End Sub End Module ' The example displays the following output: '       Not all elements end with an integer.

In both cases, the TrueForAll 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.

Note

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.

Remarks

The Predicate<T> is a delegate to a method that returnstrue 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.

Applies to

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