VerifyXMLDocument.cs

/// <summary>
/// Verify the integrity of the signed XML document
/// </summary>
/// <param name="xmlFilePath">Path to the signed xml document</param>
/// <param name="certificate">X509Certificate2 Public key certificate</param>
/// <returns></returns>
private static bool VerifyXMLDocument(string xmlFilePath, X509Certificate2 certificate)
{
    var xmlDocument = ReadXMLDocumentFromPath(xmlFilePath);

    var signedXml = new SignedXml(xmlDocument);

    // Load the XML Signature
    var nodeList = xmlDocument.GetElementsByTagName("Signature");

    signedXml.LoadXml((XmlElement)nodeList[0]);

    // Verify the integrity of the xml document
    using (var rsaKey = certificate.PublicKey.Key)
    {
        return signedXml.CheckSignature(rsaKey);
    }
}