Regex.Replace Method (String, String)

Within a specified input string, replaces all strings that match a regular expression pattern with a specified replacement string.

Namespace: System.Text.RegularExpressions
Assembly: System (in system.dll)

public string Replace (
	string input,
	string replacement
public String Replace (
	String input, 
	String replacement
public function Replace (
	input : String, 
	replacement : String
) : String
Not applicable.



The string to search for a match.


The replacement string.

Return Value

A new string that is identical to the input string, except that a replacement string takes the place of each matched string.

Exception typeCondition


input is a null reference (Nothing in Visual Basic).


replacement is a null reference (Nothing in Visual Basic).

The search for matches starts at the beginning of the input parameter string. The regular expression is the pattern defined by the constructor for the current Regex object.

The following code example demonstrates the Regex.Replace method.

// This code example demonstrates the System.Text.Regular-
// Expressions.Regex.Replace(String, String) method.

using System;
using System.Text.RegularExpressions;

class Sample 
    public static void Main() 
// Create a regular expression that matches a series of one 
// or more white spaces.
    string pattern = @"\s+";
    Regex rgx = new Regex(pattern);

// Declare a string consisting of text and white spaces.
    string inputStr = "a   b   c   d";

// Replace runs of white space in the input string with a
// comma and a blank.
    string outputStr = rgx.Replace(inputStr, ", ");

// Display the resulting string.
    Console.WriteLine("Pattern:       \"{0}\"", pattern);
    Console.WriteLine("Input string:  \"{0}\"", inputStr);
    Console.WriteLine("Output string: \"{0}\"", outputStr);
This code example produces the following results:

Pattern:       "\s+"
Input string:  "a   b   c   d"
Output string: "a, b, c, d"


Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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