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String.Compare Method (String, String)

Updated: January 2011

Compares two specified String objects and returns an integer that indicates their relationship to one another in the sort order.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
public static int Compare(
	string strA,
	string strB
)

Parameters

strA
Type: System.String

The first String.

strB
Type: System.String

The second String.

Return Value

Type: System.Int32
A 32-bit signed integer indicating the lexical relationship between the two comparands.

Value

Condition

Less than zero

strA is less than strB.

Zero

strA equals strB.

Greater than zero

strA is greater than strB.

The comparison uses the current culture to obtain culture-specific information such as casing rules and the alphabetic order of individual characters. For example, a culture could specify that certain combinations of characters be treated as a single character, or uppercase and lowercase characters be compared in a particular way, or that the sorting order of a character depends on the characters that precede or follow it.

The comparison is performed using word sort rules. For more information about word, string, and ordinal sorts, see System.Globalization.CompareOptions.

Caution noteCaution:

When comparing strings, you should call the Compare method, which requires that you explicitly specify the type of string comparison that the method uses.

One or both comparands can be null. By definition, any string, including the empty string (""), compares greater than a null reference; and two null references compare equal to each other.

The comparison terminates when an inequality is discovered or both strings have been compared. However, if the two strings compare equal to the end of one string, and the other string has characters remaining, then the string with remaining characters is considered greater. The return value is the result of the last comparison performed.

Unexpected results can occur when comparisons are affected by culture-specific casing rules. For example, in Turkish, the following example yields the wrong results because the file system in Turkish does not use linguistic casing rules for the letter 'i' in "file".

static bool IsFileURI(String path)
{
    return (String.Compare(path, 0, "file:", 0, 5, true) == 0);
}

Compare the path name to "file" using an ordinal comparison. The correct code to do this is as follows:

static bool IsFileURI(String path)
{
    return (String.Compare(path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) == 0);
}

In the following example, the ReverseStringComparer class demonstrates how you can evaluate two strings with the Compare method.

using System;
using System.Text;
using System.Collections;

public class SamplesArrayList  {

	public static void Main()  {
		// Creates and initializes a new ArrayList.
		ArrayList myAL = new ArrayList();
		myAL.Add("Eric");
		myAL.Add("Mark");
		myAL.Add("Lance");
		myAL.Add("Rob");
		myAL.Add("Kris");
		myAL.Add("Brad");
		myAL.Add("Kit");
		myAL.Add("Bradley");
		myAL.Add("Keith");
		myAL.Add("Susan");
	
		// Displays the properties and values of	the	ArrayList.
		Console.WriteLine( "Count: {0}", myAL.Count );
		
		PrintValues ("Unsorted", myAL );
		myAL.Sort();
		PrintValues("Sorted", myAL );
		myAL.Sort(new ReverseStringComparer() );
		PrintValues ("Reverse" , myAL );


		string [] names = (string[]) myAL.ToArray (typeof(string));


	}
	public static void PrintValues(string title, IEnumerable	myList )  {
		Console.Write ("{0,10}: ", title);
		StringBuilder sb = new StringBuilder();
		foreach (string s in myList) {
			sb.AppendFormat( "{0}, ", s);
		}
		sb.Remove (sb.Length-2,2);
		Console.WriteLine(sb);
	}
}
public class ReverseStringComparer : IComparer {
   public int Compare (object x, object y) {
	   string s1 = x as string;
	   string s2 = y as string;	  
	   //negate the return value to get the reverse order 
	   return - String.Compare (s1,s2);

   }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

January 2011

Added the recommendation to use an overload that has a StringComparison parameter.

Information enhancement.

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