StringCollection.IndexOf(String) Method
Definition
Important
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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 -> intPublic Function IndexOf (value As String) As IntegerParameters
- value
- String
The string to locate. The value can be null.
Returns
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.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
void PrintValues( IEnumerable^ myCol );
int main()
{
// Creates and initializes a new StringCollection.
StringCollection^ myCol = gcnew StringCollection;
array<String^>^myArr = {"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\"." );
}
void PrintValues( IEnumerable^ myCol )
{
IEnumerator^ myEnum = myCol->GetEnumerator();
while ( myEnum->MoveNext() )
{
Object^ obj = safe_cast<Object^>(myEnum->Current);
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.
*/
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.
Starting with the .NET Framework 2.0, this method uses the collection's objects' Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.
