Question

I am a beginner with .NET environment.
I have a windows application with three textboxes and one button. When the user clicks on the button, i want all the textbox values to be serialized in an XML format to a file.
I tried doing it this way,

    DialogResult dr = new DialogResult();
    private void button1_Click(object sender, EventArgs e)
    {
        AddCustomer customer = new AddCustomer();
        customer.textBox1.Text = textBox1.Text;
        customer.textBox2.Text = textBox2.Text;
        customer.textBox3.Text = textBox3.Text;
        customer.textBox4.Text = textBox4.Text;

            saveFileDialog1.InitialDirectory = @"D:";
            saveFileDialog1.Filter = "Xml Files | *.xml";
            if (saveFileDialog1.ShowDialog().Equals(DialogResult.OK))
            {

                SerializeToXML(customer);
            }            
    }

    public void SerializeToXML(AddCustomer customer)
    {

           XmlSerializer serializer = new XmlSerializer(typeof(AddCustomer));
            TextWriter textWriter = new StreamWriter(@"D:\customer.xml");
            serializer.Serialize(textWriter, customer);
            textWriter.Close();
    }

this returned system.invalidoperationexception was unhandled exception

any ideas?
Thanks,
Michael

Answer 1

There are a lot of ways to write XML in .NET. Here is a way using XmlWriter that works for very simple content like in this case:

string text1 = /* get value of textbox */;
string text2 = /* get value of textbox */;
string text3 = /* get value of textbox */;

// Set indent=true so resulting file is more 'human-readable'
XmlWriterSettings settings = new XmlWriterSettings() { Indent = true };

// Put writer in using scope; after end of scope, file is automatically saved.
using (XmlWriter writer = XmlTextWriter.Create("file.xml", settings))
{
    writer.WriteStartDocument();
    writer.WriteStartElement("root");
    writer.WriteElementString("text1", text1);
    writer.WriteElementString("text2", text2);
    writer.WriteElementString("text3", text3);
    writer.WriteEndElement();
}

One note: you should avoid doing file operations on the UI thread as this can result in blocking behavior (e.g. the disk can be slow and cause the UI to freeze up while it writes the file, or it could be writing to a network location and hang for a while as it connects). It is best to put up a progress dialog and display a message “Please wait while file is saved…” and do the file operation in the background; a simple way is to post the background operation the thread pool using BeginInvoke/EndInvoke.

---

If you want to use the XmlSerializer instead, then you would follow these steps:

1. Create a public type to act as the root element of your document and mark it with XmlRoot.
2. Add elements/attributes made of either primitive/built-in types or your own public custom types which are also XML serializable, marking them with XmlElement or XmlAttribute as necessary.
3. To write the data out, use XmlSerializer.Serialize with an appropriate Stream, StreamWriter, or XmlWriter along with your root object.
4. To read the data back in, use XmlSerializer.Deseralize with an appropriate Stream, TextReader, or XmlReader, casting the return type back to your root object.

Full sample.

The type to serialize:

[XmlRoot("customer")]
public class CustomerData
{
    // Must have a parameterless public constructor
    public CustomerData()
    {
    }

    [XmlElement("name")]
    public string Name { get; set; }

    [XmlElement("city")]
    public string City { get; set; }

    [XmlElement("company")]
    public string Company { get; set; }

    public override string ToString()
    {
        return
            "Name=[" + this.Name + "] " +
            "City=[" + this.City + "] " +
            "Company=[" + this.Company + "]";
    }
}

The code to read/write the data:

// Initialize the serializer to write and read the data
XmlSerializer serializer = new XmlSerializer(typeof(CustomerData));

// Initialize the data to serialize
CustomerData dataToWrite = new CustomerData()
{
    Name = "Joel Spolsky",
    City = "New York",
    Company = "Fog Creek Software"
};

// Write it out
XmlWriterSettings settings = new XmlWriterSettings() { Indent = true };
using (XmlWriter writer = XmlTextWriter.Create("customer.xml", settings))
{
    serializer.Serialize(writer, dataToWrite);
}

// Read it back in
CustomerData dataFromFile = null;
using (XmlReader reader = XmlTextReader.Create("customer.xml"))
{
    dataFromFile = (CustomerData)serializer.Deserialize(reader);
}

Console.WriteLine(dataFromFile);