• Article

CompareInfo.IsPrefix Method (String, String)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Determines whether the specified source string starts with the specified prefix.

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

Syntax

'Declaration
Public Overridable Function IsPrefix ( _
    source As String, _
    prefix As String _
) As Boolean

public virtual bool IsPrefix(
    string source,
    string prefix
)

Parameters

  • prefix
    Type: System.String
    The string to compare with the beginning of source.

Return Value

Type: System.Boolean
true if the length of prefix is less than or equal to the length of source and source starts with prefix; otherwise, false.

Exceptions

Exception Condition
ArgumentNullException

source is nulla null reference (Nothing in Visual Basic).

-or-

prefix is nulla null reference (Nothing in Visual Basic).

Remarks

Every string starts and ends with an empty substring (""); therefore, if prefix is an empty string, this method returns true.

Examples

The following example determines whether a string is the prefix or suffix of another string.

Imports System.Globalization

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Defines the strings to compare.
      Dim myStr1 As [String] = "calle"
      Dim myStr2 As [String] = "llegar"
      Dim myXfix As [String] = "lle"

      ' Uses the CompareInfo property of the InvariantCulture.
      Dim myComp As CompareInfo = CultureInfo.InvariantCulture.CompareInfo

      ' Determines whether myXfix is a prefix of "calle" and "llegar".
      outputBlock.Text += String.Format("IsPrefix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsPrefix(myStr1, myXfix)) & vbCrLf
      outputBlock.Text += String.Format("IsPrefix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsPrefix(myStr2, myXfix)) & vbCrLf

      ' Determines whether myXfix is a suffix of "calle" and "llegar".
      outputBlock.Text += String.Format("IsSuffix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsSuffix(myStr1, myXfix)) & vbCrLf
      outputBlock.Text += String.Format("IsSuffix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsSuffix(myStr2, myXfix)) & vbCrLf

   End Sub 'Main 

End Class 'SamplesCompareInfo


'This code produces the following output.
'
'IsPrefix( calle, lle ) : False
'IsPrefix( llegar, lle ) : True
'IsSuffix( calle, lle ) : True
'IsSuffix( llegar, lle ) : False


using System;
using System.Globalization;

public class Example
{

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

      // Defines the strings to compare.
      String myStr1 = "calle";
      String myStr2 = "llegar";
      String myXfix = "lle";

      // Uses the CompareInfo property of the InvariantCulture.
      CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo;

      // Determines whether myXfix is a prefix of "calle" and "llegar".
      outputBlock.Text += String.Format("IsPrefix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsPrefix(myStr1, myXfix)) + "\n";
      outputBlock.Text += String.Format("IsPrefix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsPrefix(myStr2, myXfix)) + "\n";

      // Determines whether myXfix is a suffix of "calle" and "llegar".
      outputBlock.Text += String.Format("IsSuffix( {0}, {1} ) : {2}", myStr1, myXfix, myComp.IsSuffix(myStr1, myXfix)) + "\n";
      outputBlock.Text += String.Format("IsSuffix( {0}, {1} ) : {2}", myStr2, myXfix, myComp.IsSuffix(myStr2, myXfix)) + "\n";

   }

}


/*
This code produces the following output.

IsPrefix( calle, lle ) : False
IsPrefix( llegar, lle ) : True
IsSuffix( calle, lle ) : True
IsSuffix( llegar, lle ) : False

*/

Version Information

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

Platforms

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