无法使用XML序列化程序反序列化多个对象，得到InvalidOperationException

我有一个简单的类Cust，我想使用XML序列化来序列化它。

public class Cust
{
public string CustName;
public int ID;
public Cust() { }
public Cust(string nm, int id)
{
CustName = nm;
ID = id;
}
public string DisInfo()
{
return CustName+" "+ID;
}
}

我的序列化函数是：

private void button1_Click(object sender, EventArgs e)
{
//Serialize
FileStream fs = new FileStream(@"C:'tmp'cust.xml", FileMode.Create);
XmlSerializer xs = new XmlSerializer(typeof(Cust));
Cust c1 = new Cust("Rahul S",111);
Cust c2 = new Cust("John D", 222);
xs.Serialize(fs, c1);
xs.Serialize(fs, c2);
fs.Close();
}

输出为cust.xml

<?xml version="1.0"?>
<Cust xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <CustName>Rahul S</CustName>
  <ID>111</ID>
</Cust><?xml version="1.0"?>
<Cust xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <CustName>John D</CustName>
  <ID>222</ID>
</Cust>

然后我尝试反序列化；从xml文件中获取Cust对象

private void button2_Click(object sender, EventArgs e)
{
//Deserialize
FileStream fs = new FileStream(@"C:'tmp'cust.xml", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
XmlSerializer xs = new XmlSerializer(typeof(Cust));
Cust c1 = (Cust)xs.Deserialize(fs);//Exception
Cust c2 = (Cust)xs.Deserialize(fs);
fs.Close();
}

这引发了的异常

InvalidOperationException未处理-XML文档（5,10）中出现错误

我知道如果我把多个对象放在一个集合中，我可以存储它们。

但在这种情况下，我将无法将列表附加到xml文件中。我想单独序列化多个对象，并逐个序列化；那么我想反序列化它们。