String.Replace Method (String, String)

.NET Framework 4.6 and 4.5

Returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string.

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

Syntax

C++

JScript

public string Replace(
	string oldValue,
	string newValue
)

Parameters

oldValue: Type: System.String
The string to be replaced.

newValue: Type: System.String
The string to replace all occurrences of oldValue.

Return Value

Type: System.String
A string that is equivalent to the current string except that all instances of oldValue are replaced with newValue. If oldValue is not found in the current instance, the method returns the current instance unchanged.

Exceptions

Exception	Condition
ArgumentNullException	oldValue is null.
ArgumentException	oldValue is the empty string ("").

Remarks

If newValue is null, all occurrences of oldValue are removed.

Note
This method does not modify the value of the current instance. Instead, it returns a new string in which all occurrences of oldValue are replaced by newValue.

This method performs an ordinal (case-sensitive and culture-insensitive) search to find oldValue.

Because this method returns the modified string, you can chain together successive calls to the Replace method to perform multiple replacements on the original string. Method calls are executed from left to right. The following example provides an illustration.

using System;

public class Example
{
   public static void Main()
   {
      String s = "aaa";
      Console.WriteLine("The initial string: '{0}'", s);
      s = s.Replace("a", "b").Replace("b", "c").Replace("c", "d");
      Console.WriteLine("The final string: '{0}'", s);
   }
}
// The example displays the following output: 
//       The initial string: 'aaa' 
//       The final string: 'ddd'

Examples

The following example demonstrates how you can use the Replace method to correct a spelling error.

C++

using System;

public class ReplaceTest {
    public static void Main() {

        string errString = "This docment uses 3 other docments to docment the docmentation";

        Console.WriteLine("The original string is:{0}'{1}'{0}", Environment.NewLine, errString);

        // Correct the spelling of "document".

        string correctString = errString.Replace("docment", "document");

        Console.WriteLine("After correcting the string, the result is:{0}'{1}'",
                Environment.NewLine, correctString);
    }
}
// 
// This code example produces the following output: 
// 
// The original string is: 
// 'This docment uses 3 other docments to docment the docmentation' 
// 
// After correcting the string, the result is: 
// 'This document uses 3 other documents to document the documentation' 
//