Verify XML data Signature Failed!

My Code:

       private bool VerifyDataSignature(XmlDocument document)
        {
            bool result = true;
            X509Certificate2 certificate;
            XmlNodeList nodeList;

            nodeList = document.GetElementsByTagName("509Certificate");
            if (nodeList == null)
            {
                return false;
            }

            certificate = new X509Certificate2(Convert.FromBase64String(((XmlNode)nodeList[0]).InnerText));
            if (certificate == null)
            {
                return false;
            }

            nodeList = document.GetElementsByTagName("Signature");
            if (nodeList.Count <= 0)
            {
                throw new CryptographicException("Verification failed: No Signature was found in the document.");
            }
            if (nodeList.Count >= 2)
            {
                throw new CryptographicException("Verification failed: More that one signature was found for the document.");
            }

            SignedXml signedXml = new SignedXml(document);
            signedXml.LoadXml((XmlElement)nodeList[0]);
            try
            {
                result = signedXml.CheckSignature(certificate, false);
                return result;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return false;
            }
        }

Error Code:

Malformed reference element.

Can you tell me why and how to correct it? or can you give me a sample code if you think my code is wrong.

Attaching XML Signature element:

<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">

<SignedInfo>

<CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />

<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />

<Reference   URI="#_518e1526-59d7-48e4-b1fb-a9a0887e2bcf">

<Transforms>

<Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />

<Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" /><

/Transforms>

<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />

<DigestValue>7v4qo9SxATgIhk+VbDd0GeIbGA8=</DigestValue>

</Reference>

</SignedInfo>

<SignatureValue>

R4ey3rTZ9oKNUlk2TXN3XVChT0mdOdPa3Z92b+lXkPeJ3oqSfOi0Q3cZrnCXyE6+pdOQ9NsWy+wqoyctGl8x0uGxJdGN9zRw+FC5lFk/cQiLtsovYA73MC4vYKPoP32VZ3BedSyd0CP+nIKA8xIBLmFE12KUeJTS/O+0LCQyeC8HVpFd8d5T/pxy+XanMyJ00LRRT60gIlG9WibKmwtpinm5QXSt+V4JPCvnHjjiC8IUOhGhAm4zhEigEnm+YKtcgb9IjhNhKkBPX1HQa1yGDkdBcEK2euoS8rdjtKWiZPKHxWY/Tny+5l8STeYZeA4T35+FmUyNu+ZRpOC5SqF2CQ==

</SignatureValue>

<KeyInfo>

<X509Data>

<X509Certificate>

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

</X509Certificate>

</X509Data>

</KeyInfo>

</Signature>