How to encode and decode a base64 string in C#

To encode a string to Base64, you first need to convert the string to a byte array and then use the Convert.ToBase64String method.

// c# base64 encode byte array
public string Base64Encode(string plainText)
{
    var data = System.Text.Encoding.UTF8.GetBytes(plainText);
    return System.Convert.ToBase64String(data);
}

In this example:

• Encoding.UTF8.GetBytes(plainText) converts the string to a byte array using UTF-8 encoding.
• Convert.ToBase64String(plainTextBytes) encodes the byte array into a Base64 string.

How to decode a base64 string in c#?

To decode a Base64 string, you can use Convert.FromBase64String to get a byte array and then convert it back to a string if necessary.

// encode decode base64 c# example
public string Base64Decode(string base64Data)
{
    var base64Bytes = System.Convert.FromBase64String(base64Data);
    return System.Text.Encoding.UTF8.GetString(base64Bytes);
}

In this example:

• Convert.FromBase64String(base64Encoded) converts the Base64 string back into a byte array.
• Encoding.UTF8.GetString(base64EncodedBytes) converts the byte array back into a regular string.

Test:

// Example string to encode
string originalString = "Hello, World!";

// Encode the string to Base64
string encodedString = EncodeToBase64(originalString);
Console.WriteLine("Encoded: " + encodedString);

// Decode the Base64 string back to the original string
string decodedString = DecodeFromBase64(encodedString);
Console.WriteLine("Decoded: " + decodedString);

Output:

Encoded: SGVsbG8sIFdvcmxkIQ==
Decoded: Hello, World!