Tuesday, June 9, 2009

Small Things Refreshed Today

I had to write a small Windows Forms application today. It just gets some user input, creates an XML file, sends it to the webservice, gets the response, parces it and shows the results to the user. Good thing is that I had to remind myself how to use two simple things.

1. Saving and retrieving values using the app.config file.

If I want to get some values from the app.config file, I can keep them in the appSetting section and the whole app.config file for the small application can be as simple as that

To read the values I need to do just the following (after I add a reference to System.configuration to the project):

string myFirstValue = ConfigurationManager.AppSettings.Get("MYKEY1");

To update the values I need to put a little bit more effort

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
AppSettingsSection appSettings = config.AppSettings;

appSettings.Settings["MYKEY1"].Value = myNewValue1;
appSettings.Settings["MYKEY2"].Value = myNewValue2;


It is useful to know that this would not work at debug time, though - it will not throw an exception, but the values would not be updated too. I spent a few minutes trying to find out why it does not work before I understood that this behaviour is expected.

2. Creating the XML document.

Of course, for the purposes of my application, where the whole XML is maybe 10 to 15 elements, I could go with the following:

string myXML = "
myXML += "" + someID + "";
myXML += "";
return myXML;

The code would actually be shorter than the "proper" XML handling, take less time to write and maybe even will work faster (especially if I use a StringBuilder to concatenate strings). I did it the "proper" way, however - for practice.

To create a document

XmlDocument xmlDoc = new XmlDocument();

To create a declaration

XmlDeclaration xDec = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);

To create an element in a format of

I created a small helper function

private XmlElement CreateElementFromNameValue(string name, string value)
XmlElement element = xmlDoc.CreateElement(name);
element.InnerText = value;
return element;

To create an attribute to the element

XmlElement xmlHeader = xmlDoc.CreateElement("header");
XmlAttribute schema = xmlDoc.CreateAttribute("SchemaVersion");
schema.Value = "2.0";

To bring it all together

XmlDocument xmlDoc = new XmlDocument();
XmlDeclaration xDec = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);

XmlElement request = xmlDoc.CreateElement("request");
XmlAttribute schema = xmlDoc.CreateAttribute("SchemaVersion");
schema.Value = "2.0";

request.AppendChild(CreateElementFromNameValue("MYKEY1", "myValue1"));
request.AppendChild(CreateElementFromNameValue("MYKEY2", "myValue2"));


Expected InnerXml of the xmlDoc

by . Also posted on my website

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