/// <summary>
/// To demonstrate extraction of file extension from base64 string.
/// </summary>
/// <param name="base64String">base64 string.</param>
/// <returns>Henceforth file extension from string.</returns>
public static string GetFileExtension(string base64String)
{
var data = base64String.Substring(0, 5);
switch (data.ToUpper())
{
case "IVBOR":
return "png";
case "/9J/4":
return "jpg";
case "AAAAF":
return "mp4";
case "JVBER":
return "pdf";
case "AAABA":
return "ico";
case "UMFYI":
return "rar";
case "E1XYD":
return "rtf";
case "U1PKC":
return "txt";
case "MQOWM":
case "77U/M":
return "srt";
default:
return string.Empty;
}
}