C# program to replace all spaces in a string with '%20'

When working with strings in C#, you may need to replace spaces with '%20' for URL encoding or other formatting purposes. The Replace() method provides a simple way to substitute all occurrences of a character or substring with another value.

Syntax

Following is the syntax for using the Replace() method −

string newString = originalString.Replace(oldValue, newValue);

Parameters

• oldValue − The string or character to be replaced

• newValue − The string or character to replace with

Return Value

The method returns a new string with all occurrences of the specified value replaced. The original string remains unchanged since strings are immutable in C#.

Example

Following example demonstrates how to replace all spaces in a string with '%20' −

using System;

class Demo {
    static void Main() {
        string str = "Hello World !";
        Console.WriteLine("Original String: " + str);
        
        string str2 = str.Replace(" ", "%20");
        Console.WriteLine("String (After replacing): " + str2);
    }
}

The output of the above code is −

Original String: Hello World !
String (After replacing): Hello%20World%20!

Using Replace() for URL Encoding

Replacing spaces with '%20' is commonly used in URL encoding. Here's a more practical example −

using System;

class URLEncoder {
    static void Main() {
        string[] urls = {
            "My Document.pdf",
            "Hello World Page.html",
            "User Profile Settings.aspx"
        };
        
        Console.WriteLine("URL Encoding Examples:");
        Console.WriteLine("----------------------");
        
        foreach (string url in urls) {
            string encodedUrl = url.Replace(" ", "%20");
            Console.WriteLine("Original: " + url);
            Console.WriteLine("Encoded:  " + encodedUrl);
            Console.WriteLine();
        }
    }
}

The output of the above code is −

URL Encoding Examples:
----------------------
Original: My Document.pdf
Encoded:  My%20Document.pdf

Original: Hello World Page.html
Encoded:  Hello%20World%20Page.html

Original: User Profile Settings.aspx
Encoded:  User%20Profile%20Settings.aspx

Multiple Character Replacement

You can also replace multiple types of characters by chaining Replace() methods −

using System;

class MultipleReplace {
    static void Main() {
        string text = "Hello World! How are you?";
        Console.WriteLine("Original: " + text);
        
        string encoded = text.Replace(" ", "%20")
                            .Replace("!", "%21")
                            .Replace("?", "%3F");
        
        Console.WriteLine("Encoded:  " + encoded);
    }
}

The output of the above code is −

Original: Hello World! How are you?
Encoded:  Hello%20World%21%20How%20are%20you%3F

Conclusion

The Replace()