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StringCollection.IndexOf(String) Method

Definition

Namespace:
System.Collections.Specialized
Assemblies:
System.dll, System.Collections.Specialized.dll
Assemblies:
netstandard.dll, System.Collections.Specialized.dll
Assembly:
System.Collections.Specialized.dll
Assembly:
System.dll
Assembly:
netstandard.dll
Source:
StringCollection.cs
Source:
StringCollection.cs
Source:
StringCollection.cs
Source:
StringCollection.cs

Searches for the specified string and returns the zero-based index of the first occurrence within the StringCollection.

public:
 int IndexOf(System::String ^ value);
public int IndexOf(string value);
public int IndexOf(string? value);
member this.IndexOf : string -> int
Public Function IndexOf (value As String) As Integer

Parameters

value
String

The string to locate. The value can be null.

Returns

Int32

The zero-based index of the first occurrence of value in the StringCollection, if found; otherwise, -1.

Examples

The following code example searches the StringCollection for an element.

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesStringCollection  {

   public static void Main()  {

      // Creates and initializes a new StringCollection.
      StringCollection myCol = new StringCollection();
      String[] myArr = new String[] { "RED", "orange", "yellow", "RED", "green", "blue", "RED", "indigo", "violet", "RED" };
      myCol.AddRange( myArr );

      Console.WriteLine( "Initial contents of the StringCollection:" );
      PrintValues( myCol );

      // Checks whether the collection contains "orange" and, if so, displays its index.
      if ( myCol.Contains( "orange" ) )
         Console.WriteLine( "The collection contains \"orange\" at index {0}.", myCol.IndexOf( "orange" ) );
      else
         Console.WriteLine( "The collection does not contain \"orange\"." );
   }

   public static void PrintValues( IEnumerable myCol )  {
      foreach ( Object obj in myCol )
         Console.WriteLine( "   {0}", obj );
      Console.WriteLine();
   }
}

/*
This code produces the following output.

Initial contents of the StringCollection:
   RED
   orange
   yellow
   RED
   green
   blue
   RED
   indigo
   violet
   RED

The collection contains "orange" at index 1.

*/

Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringCollection   

   Public Shared Sub Main()

      ' Creates and initializes a new StringCollection.
      Dim myCol As New StringCollection()
      Dim myArr() As [String] = {"RED", "orange", "yellow", "RED", "green", "blue", "RED", "indigo", "violet", "RED"}
      myCol.AddRange(myArr)

      Console.WriteLine("Initial contents of the StringCollection:")
      PrintValues(myCol)

      ' Checks whether the collection contains "orange" and, if so, displays its index.
      If myCol.Contains("orange") Then
         Console.WriteLine("The collection contains ""orange"" at index {0}.", myCol.IndexOf("orange"))
      Else
         Console.WriteLine("The collection does not contain ""orange"".")
      End If 

   End Sub

   Public Shared Sub PrintValues(myCol As IEnumerable)
      Dim obj As [Object]
      For Each obj In  myCol
         Console.WriteLine("   {0}", obj)
      Next obj
      Console.WriteLine()
   End Sub

End Class


'This code produces the following output.
'
'Initial contents of the StringCollection:
'   RED
'   orange
'   yellow
'   RED
'   green
'   blue
'   RED
'   indigo
'   violet
'   RED
'
'The collection contains "orange" at index 1.
'

Remarks

This method determines equality by calling Object.Equals. String comparisons are case-sensitive.

This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

This method uses the collection's objects' Equals and CompareTo methods on item to determine whether item exists.

Applies to

See also