BinarySearch Method (Array, Object)

Array.BinarySearch Method (Array, Object)

.NET Framework 1.1

Searches an entire one-dimensional sorted Array for a specific element, using the IComparable interface implemented by each element of the Array and by the specified object.

[Visual Basic]
Overloads Public Shared Function BinarySearch( _
   ByVal array As Array, _
   ByVal value As Object _
) As Integer
[C#]
public static int BinarySearch(
 Array array,
 object value
);
[C++]
public: static int BinarySearch(
 Array* array,
 Object* value
);
[JScript]
public static function BinarySearch(
   array : Array,
 value : Object
) : int;

Parameters

array
The one-dimensional Array to search.
value
The object to search for.

Return Value

The index of the specified value in the specified array, if value is found.

-or-

A negative number, which is the bitwise complement of the index of the first element that is larger than value, if value is not found and value is less than one or more elements in array.

-or-

A negative number, which is the bitwise complement of (the index of the last element + 1), if value is not found and value is greater than any of the elements in array.

Exceptions

Exception Type Condition
ArgumentNullException array is a null reference (Nothing in Visual Basic).
RankException array is multidimensional.
ArgumentException value is of a type that is not compatible with the elements of array.
InvalidOperationException Neither value nor the elements of array implement the IComparable interface.

Remarks

Either value or every element of array must implement the IComparable interface, which is used for comparisons. If the elements of array are not already sorted in increasing value according to the IComparable implementation, the result might be incorrect.

Duplicate elements are allowed. If the Array contains more than one element equal to value, the method returns the index of only one of the occurrences, and not necessarily the first one.

A null reference (Nothing in Visual Basic) can always be compared with any other type; therefore, comparisons with a null reference (Nothing) do not generate an exception. When sorting, a null reference (Nothing) is considered to be less than any other object.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~) to a negative result to produce the index of the first element, if any, that is larger than the specified search value.

Example

The following code example shows how to use BinarySearch to locate a specific object in an Array.

[Visual Basic] 
Imports System
Imports Microsoft.VisualBasic

Public Class SamplesArray    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new Array.
        Dim myIntArray As Array = Array.CreateInstance(GetType(Int32), 5)
        Dim i As Integer
        For i = myIntArray.GetLowerBound(0) To myIntArray.GetUpperBound(0)
            myIntArray.SetValue(i * 2, i)
        Next i 
        ' Displays the values of the Array.
        Console.WriteLine("The Int32 array contains the following:")
        PrintValues(myIntArray)
        
        ' Locates a specific object that does not exist in the Array.
        Dim myObjectOdd As Object = 3
        FindMyObject(myIntArray, myObjectOdd)
        
        ' Locates an object that exists in the Array.
        Dim myObjectEven As Object = 6
        FindMyObject(myIntArray, myObjectEven)
    End Sub
    
    
    Public Shared Sub FindMyObject(myArr As Array, myObject As Object)
        Dim myIndex As Integer = Array.BinarySearch(myArr, myObject)
        If myIndex < 0 Then
            Console.WriteLine("The object to search for ({0}) is not found. " _
               + "The next larger object is at index {1}.", myObject, Not(myIndex))
        Else
            Console.WriteLine("The object to search for ({0}) is at index " _
               + "{1}.", myObject, myIndex)
        End If
    End Sub
     
    
    Public Shared Sub PrintValues(myArr As Array)
        Dim myEnumerator As System.Collections.IEnumerator = _
           myArr.GetEnumerator()
        Dim i As Integer = 0
        Dim cols As Integer = myArr.GetLength((myArr.Rank - 1))
        While myEnumerator.MoveNext()
            If i < cols Then
                i += 1
            Else
                Console.WriteLine()
                i = 1
            End If
            Console.Write(ControlChars.Tab + "{0}", myEnumerator.Current)
        End While
        Console.WriteLine()
    End Sub
End Class

' This code produces the following output.
' 
' The Int32 array contains the following:
'     0    2    4    6    8
' The object to search for (3) is not found. The next larger object is at index 2.
' The object to search for (6) is at index 3.  

[C#] 
using System;
public class SamplesArray  {

   public static void Main()  {

      // Creates and initializes a new Array.
      Array myIntArray = Array.CreateInstance( typeof(Int32), 5 );
      for ( int i = myIntArray.GetLowerBound(0); i <= myIntArray.GetUpperBound(0); i++ )
         myIntArray.SetValue( i*2, i );

      // Displays the values of the Array.
      Console.WriteLine( "The Int32 array contains the following:" );
      PrintValues( myIntArray );

      // Locates a specific object that does not exist in the Array.
      Object myObjectOdd = 3;
      FindMyObject( myIntArray, myObjectOdd );

      // Locates an object that exists in the Array.
      Object myObjectEven = 6;
      FindMyObject( myIntArray, myObjectEven );
   }

   public static void FindMyObject( Array myArr, Object myObject )  {
      int myIndex=Array.BinarySearch( myArr, myObject );
      if ( myIndex < 0 )
         Console.WriteLine( "The object to search for ({0}) is not found. The next larger object is at index {1}.", myObject, ~myIndex );
      else
         Console.WriteLine( "The object to search for ({0}) is at index {1}.", myObject, myIndex );
   }


   public static void PrintValues( Array myArr )  {
      System.Collections.IEnumerator myEnumerator = myArr.GetEnumerator();
      int i = 0;
      int cols = myArr.GetLength( myArr.Rank - 1 );
      while ( myEnumerator.MoveNext() )  {
         if ( i < cols )  {
            i++;
         } else  {
            Console.WriteLine();
            i = 1;
         }
         Console.Write( "\t{0}", myEnumerator.Current );
      }
      Console.WriteLine();
   }
}
/* 
This code produces the following output.

The Int32 array contains the following:
    0    2    4    6    8
The object to search for (3) is not found. The next larger object is at index 2.
The object to search for (6) is at index 3.
 */

[C++] 
#using <mscorlib.dll>
using namespace System;

void FindMyObject( Array* myArr, Object* myObject );
void PrintValues( Array* myArr );

void main()  {
 
   // Creates and initializes a new Array instance.
   Array* myIntArray = Array::CreateInstance( __typeof(Int32), 5 );

   for ( int i = myIntArray->GetLowerBound(0); i <= myIntArray->GetUpperBound(0); i++ )
       myIntArray->SetValue( __box(i*2), i );
 
   // Displays the values of the Array.
   Console::WriteLine( "The Int32 array contains the following:" );
   PrintValues( myIntArray );
 
   // Locates a specific object that does not exist in the Array.
   Object* myObjectOdd = __box(3);
   FindMyObject( myIntArray, myObjectOdd );
 
   // Locates an object that exists in the Array.
   Object* myObjectEven = __box(6);
   FindMyObject( myIntArray, myObjectEven );
}
 
void FindMyObject( Array* myArr, Object* myObject )  {

   int myIndex = Array::BinarySearch( myArr, myObject );

   if ( myIndex < 0 )
    Console::WriteLine( "The object to search for ({0}) is not found. The next larger object is at index {1}.", myObject, __box(~myIndex) );
   else
    Console::WriteLine( "The object to search for ({0}) is at index {1}.", myObject, __box(myIndex) );
}
 
 
void PrintValues( Array* myArr )  {
   System::Collections::IEnumerator* myEnumerator = myArr->GetEnumerator();
   int i = 0;
   int cols = myArr->GetLength( myArr->Rank - 1 );
   while ( myEnumerator->MoveNext() )  {
    if ( i < cols )  {
        i++;
    } 
    else {
        Console::WriteLine();
        i = 1;
    }
    Console::Write( "\t{0}", myEnumerator->Current );
   }
   Console::WriteLine();
}

 /* 
 This code produces the following output.
 
 The Int32 array contains the following:
     0    2    4    6    8
 The object to search for (3) is not found. The next larger object is at index 2.
 The object to search for (6) is at index 3.
  */

[JScript] 
import System
import System.Collections

// Creates and initializes a new Array.
var myIntArray : System.Array = System.Array.CreateInstance( Int32, 5);

for ( var i : int = myIntArray.GetLowerBound(0); i <= myIntArray.GetUpperBound(0); i++ )
    myIntArray.SetValue( Int32(i*2), i );

// Displays the values of the Array.
Console.WriteLine( "The Int32 array contains the following:" );
PrintValues( myIntArray );

// Locates a specific object that does not exist in the Array.
var myObjectOdd : Object  = 3;
FindMyObject( myIntArray, myObjectOdd );

// Locates an object that exists in the Array.
var myObjectEven : Object  = 6;
FindMyObject( myIntArray, myObjectEven );


function FindMyObject( myArr : System.Array, myObject : Object)  {

    var myIndex : int = System.Array.BinarySearch( myArr, myObject );

    if ( myIndex < 0 )
        Console.WriteLine( "The object to search for ({0}) is not found. " + 
                "The next larger object is at index {1}.", myObject, ~myIndex );
    else
        Console.WriteLine( "The object to search for ({0}) is at index {1}.", myObject, myIndex );
}

function PrintValues( myArr : System.Array )  {
    var arrEnum : IEnumerator = myArr.GetEnumerator();
    arrEnum.Reset();

    while (arrEnum.MoveNext()) {            

        Console.Write( "{0,-6}", arrEnum.Current.ToString());
    }

    Console.WriteLine();

}
 /* 
 This code produces the following output.
 
 The Int32 array contains the following:
     0    2    4    6    8
 The object to search for (3) is not found. The next larger object is at index 2.
 The object to search for (6) is at index 3.
  */

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

Array Class | Array Members | System Namespace | Array.BinarySearch Overload List | IComparable | Sort | Performing Culture-Insensitive String Operations in Arrays

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