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String.CompareTo Method (String)

Compares this instance with a specified String object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified String.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public int CompareTo(
	string strB
)

Parameters

strB
Type: System.String
The string to compare with this instance.

Return Value

Type: System.Int32
A 32-bit signed integer that indicates whether this instance precedes, follows, or appears in the same position in the sort order as the value parameter.

Value

Condition

Less than zero

This instance precedes strB.

Zero

This instance has the same position in the sort order as strB.

Greater than zero

This instance follows strB.

-or-

strB is null.

Implements

IComparable<T>.CompareTo(T)

This method performs a word (case-sensitive and culture-sensitive) comparison using the current culture. For more information about word, string, and ordinal sorts, see System.Globalization.CompareOptions.

Caution noteCaution:

The CompareTo(String) method is designed primarily for use in sorting or alphabetizing operations. It should not be used when the primary purpose of the method call is to determine whether two strings are equivalent (that is, when the purpose of the method call is to test for a return value of zero). To determine whether two strings are equivalent, call the Equals method.

For more information about the behavior of this method, see the Remarks section of the Compare method.

This method implements the System.IComparable<T> interface, and performs slightly better than the String.CompareTo method because it does not have to unbox an object that contains a string.

The following code example demonstrates how you can use the CompareTo method with another String.


using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      string strFirst = "Goodbye";
      string strSecond = "Hello";
      string strThird = "a small string";
      string strFourth = "goodbye";

      // compare a string to itself
      outputBlock.Text += String.Format(CompareStrings(strFirst, strFirst)) + "\n";

      outputBlock.Text += String.Format(CompareStrings(strFirst, strSecond)) + "\n";
      outputBlock.Text += String.Format(CompareStrings(strFirst, strThird)) + "\n";

      // compare a string to another string that varies only by case
      outputBlock.Text += String.Format(CompareStrings(strFirst, strFourth)) + "\n";
      outputBlock.Text += String.Format(CompareStrings(strFourth, strFirst)) + "\n";
   }

   private static string CompareStrings(string str1, string str2)
   {

      // compare the values, using the CompareTo method on the first string
      int cmpVal = str1.CompareTo(str2);

      if (cmpVal == 0) // the values are the same
         return "The strings have the same value!";

      else if (cmpVal > 0) // the first value is greater than the second value
         return "The first string is greater than the second string!";

      else // the second string is greater than the first string
         return "The second string is greater than the first string!";
   }
}

// This code example displays the following:
//
// The strings have the same value!
// The second string is greater than the first string!
// The first string is greater than the second string!
// The first string is greater than the second string!
// The second string is greater than the first string!


The following code example demonstrates generic and non-generic versions of the CompareTo method for several value and reference types.


// This example demonstrates the generic and non-generic versions of the 
// CompareTo method for several base types.
// The non-generic version takes a parameter of type Object, while the generic
// version takes a type-specific parameter, such as Boolean, Int32, or Double.

using System;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string nl = "\n";
      string msg = "{0}The following is the result of using the generic and non-generic{0}" +
                      "versions of the CompareTo method for several base types:{0}";

      DateTime now = DateTime.Now;
      // Time span = 11 days, 22 hours, 33 minutes, 44 seconds
      TimeSpan tsX = new TimeSpan(11, 22, 33, 44);
      // Version = 1.2.333.4
      Version versX = new Version("1.2.333.4");
      // Guid = CA761232-ED42-11CE-BACD-00AA0057B223
      Guid guidX = new Guid("{CA761232-ED42-11CE-BACD-00AA0057B223}");

      Boolean a1 = true, a2 = true;
      Byte b1 = 1, b2 = 1;
      Int16 c1 = -2, c2 = 2;
      Int32 d1 = 3, d2 = 3;
      Int64 e1 = 4, e2 = -4;
      Decimal f1 = -5.5m, f2 = 5.5m;
      Single g1 = 6.6f, g2 = 6.6f;
      Double h1 = 7.7d, h2 = -7.7d;
      Char i1 = 'A', i2 = 'A';
      String j1 = "abc", j2 = "abc";
      DateTime k1 = now, k2 = now;
      TimeSpan l1 = tsX, l2 = tsX;
      Version m1 = versX, m2 = new Version("2.0");
      Guid n1 = guidX, n2 = guidX;

      // The following types are not CLS-compliant.
      SByte w1 = 8, w2 = 8;
      UInt16 x1 = 9, x2 = 9;
      UInt32 y1 = 10, y2 = 10;
      UInt64 z1 = 11, z2 = 11;
      //
      outputBlock.Text += String.Format(msg, nl) + "\n";
      try
      {
         // The second and third Show method call parameters are automatically boxed because
         // the second and third Show method declaration arguments expect type Object.

         Show(outputBlock, "Boolean:  ", a1, a2, a1.CompareTo(a2), a1.CompareTo((Object)a2));
         Show(outputBlock, "Byte:     ", b1, b2, b1.CompareTo(b2), b1.CompareTo((Object)b2));
         Show(outputBlock, "Int16:    ", c1, c2, c1.CompareTo(c2), c1.CompareTo((Object)c2));
         Show(outputBlock, "Int32:    ", d1, d2, d1.CompareTo(d2), d1.CompareTo((Object)d2));
         Show(outputBlock, "Int64:    ", e1, e2, e1.CompareTo(e2), e1.CompareTo((Object)e2));
         Show(outputBlock, "Decimal:  ", f1, f2, f1.CompareTo(f2), f1.CompareTo((Object)f2));
         Show(outputBlock, "Single:   ", g1, g2, g1.CompareTo(g2), g1.CompareTo((Object)g2));
         Show(outputBlock, "Double:   ", h1, h2, h1.CompareTo(h2), h1.CompareTo((Object)h2));
         Show(outputBlock, "Char:     ", i1, i2, i1.CompareTo(i2), i1.CompareTo((Object)i2));
         Show(outputBlock, "String:   ", j1, j2, j1.CompareTo(j2), j1.CompareTo((Object)j2));
         Show(outputBlock, "DateTime: ", k1, k2, k1.CompareTo(k2), k1.CompareTo((Object)k2));
         Show(outputBlock, "TimeSpan: ", l1, l2, l1.CompareTo(l2), l1.CompareTo((Object)l2));
         Show(outputBlock, "Version:  ", m1, m2, m1.CompareTo(m2), m1.CompareTo((Object)m2));
         Show(outputBlock, "Guid:     ", n1, n2, n1.CompareTo(n2), n1.CompareTo((Object)n2));
         //
         outputBlock.Text += String.Format("{0}The following types are not CLS-compliant:", nl) + "\n";
         Show(outputBlock, "SByte:    ", w1, w2, w1.CompareTo(w2), w1.CompareTo((Object)w2));
         Show(outputBlock, "UInt16:   ", x1, x2, x1.CompareTo(x2), x1.CompareTo((Object)x2));
         Show(outputBlock, "UInt32:   ", y1, y2, y1.CompareTo(y2), y1.CompareTo((Object)y2));
         Show(outputBlock, "UInt64:   ", z1, z2, z1.CompareTo(z2), z1.CompareTo((Object)z2));
      }
      catch (Exception e)
      {
         outputBlock.Text += e + "\n";
      }
   }

   public static void Show(System.Windows.Controls.TextBlock outputBlock, string caption, Object var1, Object var2,
                           int resultGeneric, int resultNonGeneric)
   {
      string relation;

      outputBlock.Text += caption;
      if (resultGeneric == resultNonGeneric)
      {
         if (resultGeneric < 0) relation = "less than";
         else if (resultGeneric > 0) relation = "greater than";
         else relation = "equal to";
         outputBlock.Text += String.Format("{0} is {1} {2}", var1, relation, var2) + "\n";
      }

  // The following condition will never occur because the generic and non-generic
      // CompareTo methods are equivalent.

      else
      {
         outputBlock.Text += String.Format("Generic CompareTo = {0}; non-generic CompareTo = {1}",
                            resultGeneric, resultNonGeneric) + "\n";
      }
   }
}
/*
This example produces the following results:

The following is the result of using the generic and non-generic versions of the
CompareTo method for several base types:

Boolean:  True is equal to True
Byte:     1 is equal to 1
Int16:    -2 is less than 2
Int32:    3 is equal to 3
Int64:    4 is greater than -4
Decimal:  -5.5 is less than 5.5
Single:   6.6 is equal to 6.6
Double:   7.7 is greater than -7.7
Char:     A is equal to A
String:   abc is equal to abc
DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM
TimeSpan: 11.22:33:44 is equal to 11.22:33:44
Version:  1.2.333.4 is less than 2.0
Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00
aa0057b223

The following types are not CLS-compliant:
SByte:    8 is equal to 8
UInt16:   9 is equal to 9
UInt32:   10 is equal to 10
UInt64:   11 is equal to 11
*/


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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