Check out example codes for "c# encrypt decrypt string". It will help you in understanding the concepts better.

Code Example 1

public static string Base64Decode(string base64EncodedData)
{
   var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);
   return System.Text.Encoding.UTF8.GetString(base64EncodedBytes);
}
public static string Base64Encode(string plainText)
{
   var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);
   return System.Convert.ToBase64String(plainTextBytes);
}

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