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Metodo String.Compare (String, String)

 

Confronta due oggetti String specificati e restituisce un intero che ne indica la posizione relativa nell'ordinamento.

Spazio dei nomi:   System
Assembly:  mscorlib (in mscorlib.dll)

public static int Compare(
	string strA,
	string strB
)

Parametri

strA
Type: System.String

Prima stringa da confrontare.

strB
Type: System.String

Seconda stringa da confrontare.

Valore restituito

Type: System.Int32

Intero con segno a 32 bit che indica la relazione lessicale tra i due termini di confronto.

Valore

Condizione

Minore di zero

strA precede strB nell'ordinamento.

Zero

strA si trova nella stessa posizione di strB nell'ordinamento.

Maggiore di zero

strA segue strB nell'ordinamento.

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 T:System.Globalization.CompareOptions.

System_CAPS_warningAvviso

When comparing strings, you should call theM:System.String.Compare(System.String,System.String,System.StringComparison) method, which requires that you explicitly specify the type of string comparison that the method uses. For more information, see Best Practices for Using Strings in the .NET Framework.

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);
}

Note per i chiamanti:

Character sets include ignorable characters. The M:System.String.Compare(System.String,System.String) method does not consider such characters when it performs a culture-sensitive comparison. For example, if the following code is run on the netfx40_short or later, a culture-sensitive comparison of "animal" with "ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent.

using System;

public class Example
{
   public static void Main()
   {
      string s1 = "ani\u00ADmal";
      string s2 = "animal";

      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, s2, String.Compare(s1, s2));
   }
}
// The example displays the following output:
//       Comparison of 'ani-mal' and 'animal': 0

To recognize ignorable characters in a string comparison, call the M:System.String.Compare(System.String,System.String,System.StringComparison) method and supply a value of either F:System.Globalization.CompareOptions.Ordinal or F:System.Globalization.CompareOptions.OrdinalIgnoreCase for the comparisonType parameter.

The following example calls the M:System.String.Compare(System.String,System.String) method to compare three sets of strings.

using System;

class Example
{
   static void Main()
   {
      // Create upper-case characters from their Unicode code units.
      String stringUpper = "\x0041\x0042\x0043";

      // Create lower-case characters from their Unicode code units.
      String stringLower = "\x0061\x0062\x0063";

      // Display the strings.
      Console.WriteLine("Comparing '{0}' and '{1}':", 
                        stringUpper, stringLower);

      // Compare the uppercased strings; the result is true.
      Console.WriteLine("The Strings are equal when capitalized? {0}",
                        String.Compare(stringUpper.ToUpper(), stringLower.ToUpper()) == 0 
                                       ? "true" : "false");

      // The previous method call is equivalent to this Compare method, which ignores case.
      Console.WriteLine("The Strings are equal when case is ignored? {0}",
                        String.Compare(stringUpper, stringLower, true) == 0
                                       ? "true" : "false" );
   }
} 
// The example displays the following output:
//       Comparing 'ABC' and 'abc':
//       The Strings are equal when capitalized? true
//       The Strings are equal when case is ignored? true

In the following example, the ReverseStringComparer class demonstrates how you can evaluate two strings with the M:System.String.Compare(System.String,System.String) 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);

   }
}

Universal Windows Platform
Disponibile da 8
.NET Framework
Disponibile da 1.1
Libreria di classi portabile
Supportato in: piattaforme .NET portabili
Silverlight
Disponibile da 2.0
Windows Phone Silverlight
Disponibile da 7.0
Windows Phone
Disponibile da 8.1
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