CreateAuthorizationHeader

public static String CreateAuthorizationHeader(String canonicalizedString) {
    String signature = String.Empty;

    using (HMACSHA256 hmacSha256 = new HMACSHA256( Convert.FromBase64String(storageAccountKey) )) {
        Byte[] dataToHmac = System.Text.Encoding.UTF8.GetBytes(canonicalizedString);
        signature = Convert.ToBase64String(hmacSha256.ComputeHash(dataToHmac));
    }

    String authorizationHeader = String.Format(
        CultureInfo.InvariantCulture,
        "{0} {1}:{2}",
        AzureStorageConstants.SharedKeyAuthorizationScheme,
        AzureStorageConstants.Account,
        signature
    );

    return authorizationHeader;
}