列表未正确填充

Question

Every time I run this code, certlist reads in the first set of values and writes them successfully to the list. When it runs through the loop again the next set of values overwrites the first one and creates a second one. The end result is two identically values inside the list.

Any help with why it would overwrite the first value and how to fix it would be great.

        foreach (var certcard in xdoc.Root.Element("Diver").Element("Certifications").Elements("Certification_Card"))
        {
            cert.Level = certcard.Element("Level").Value;
            cert.Agency = certcard.Element("Agency").Value;
            cert.Number = certcard.Element("Number").Value;
            cert.Date = Convert.ToDateTime(certcard.Element("Date").Value);

            certlist.Add(cert);
        }

Answer 1

Your original code was only missing the declaration of cert:

    foreach (var certcard in xdoc.Root.Element("Diver").Element("Certifications")
        .Elements("Certification_Card"))
    {
        var cert = new Cert();
        cert.Level = certcard.Element("Level").Value;
        cert.Agency = certcard.Element("Agency").Value;
        cert.Number = certcard.Element("Number").Value;
        cert.Date = Convert.ToDateTime(certcard.Element("Date").Value);

        certlist.Add(cert);
    }

Similarly, you could do this without a loop using Linq:

certlist.AddRange(xdoc.Root.Element("Diver")
    .Element("Certifications")
    .Elements("Certification_Card")
    .Select(c => new Cert
    {
        Level = c.Element("Level").Value,
        Agency = c.Element("Agency").Value,
        Number = c.Element("Number").Value,
        Date = Convert.ToDateTime(c.Element("Date").Value)
    }));

Answer 2

Try this :

    foreach (var certcard in xdoc.Root.Element("Diver").Element("Certifications")
        .Elements("Certification_Card"))
    {
        certlist.Add(new Cert() 
        { 
            Level = certcard.Element("Level").Value, 
            Agency = certcard.Element("Agency").Value, 
            Number = certcard.Element("Number").Value, 
            Date = Convert.ToDateTime(certcard.Element("Date").Value) 
        });
    }