Perhaps you are wondering now, "Pretty cool - but what if I don't want
to save my object to disk?" Another good question. There's no reason you
would have to. Let's suppose that for some reason, you needed to serialize
an object into an XML string to be used for some purpose and then forgotten
or re-instantiated or whatever else. This can be accomplished in almost the
same way that was demonstrated earlier. However, instead of using a StreamWriter object in the process, we will use a StringWriter object. See the code snippet
below:
dim oDusty as new Person()
dim oStrW as new StringWriter()
dim sXML as string
'Set properties
oDusty.Name = "Dusty Bottoms"
oDusty.Age = 51
'Serialize object into an XML string
oXS.Serialize(oStrW, oDusty)
sXML = oStrW.ToString()
oStrW.Close()
As you can see, we instantiate a new Person object and StringWriter object
and then assign values to the Name and Age properties of the Person object.
We then call the Serialize() method of the XMLSerializer object and the Person object is serialized into an XML document and placed in the StringWriter object.
Before we move on, it is important to understand some things about the StringWriter and StreamWriter objects and Inheritance. The Serialize() method of the XMLSerializer object is an overloaded method and one of its signatures is: Overloads
Public Sub Serialize(TextWriter, Object). This means we must send it a TextWriter object and some other object.
"Wait a minute!" I hear you shouting, "If it needs to be sent a TextWriter object, why are we sending it StringWriters and StreamWriters?" That's because of Inheritance. In object oriented development, objects can be derived from other objects, inheriting some or all of the original object's characteristics. This is where StringWriter and StreamWriter come from. They are "descendants" of TextWriter. Think of it this way: A man named Fritz Meyer has two children, Hansel and Gretel. Hansel is not Fritz, but he is a Meyer as is Gretel and when they have a Meyer family reunion, Fritz, Hansel, and Gretel can all get in the door because they are all Meyers. Similarly, because StreamWriter and StringWriter are both descended from TextWriter, they can be used with this call to Serialize(). Unfortunately, StreamWriter doesn't have a way to present its contents as a string data type, but StringWriter does and we are interested, at this point, in getting the XML string rather than saving it to a file. That is why, in the code snippet above, we send a StringWriter to Serialize() instead of a StreamWriter.
After the serialization takes place, we capture the XML string by calling
the ToString() method of the StringWriter object and placing the results in
a string variable. Next, we close the StringWriter object because we no longer
need it. We now have our hands on the XML string and can do with it what we
please. In the downloadable example code, all we do with it is output it to
the browser.
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