So I recently thought I’d try using the app.config file
to specify some data for my application (such as URLs) rather than hard-coding it into my app, which would require a recompile and redeploy of my app if one of our URLs changed. By using the app.config it allows a user
to just open up the .config file that sits beside their .exe file and edit the URLs right there and then re-run the app; no recompiling, no redeployment necessary. I spent a good few hours fighting with the app.config and looking at examples on Google before I was able
to get things
to work properly. Most of the examples I found showed you how
to pull a value from the app.config if you knew the specific key of the element you wanted
to retrieve, but it took me a while
to find a way
to simply loop through all elements in a section, so I thought I would share my solutions here. Simple and Easy The easiest way
to use the app.config is
to use the built-in types, such as NameValueSectionHandler. For example, if we just wanted
to add a list of database server urls
to use in my app, we could do this in the app.config file like so: 1: <?xml version="1.0" encoding="utf-8" ?>
2: <configuration>
3: <configSections>
4: <section name="ConnectionManagerDatabaseServers" type="System.Configuration.NameValueSectionHandler" />
5: </configSections>
6: <startup>
7: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
8: </startup>
9: <ConnectionManagerDatabaseServers>
10: <add key="localhost" value="localhost" />
11: <add key="Dev" value="Dev.MyDomain.
local" />
12: <add key="Test" value="Test.MyDomain.
local" />
13: <add key="Live" value="Prod.MyDomain.com" />
14: </ConnectionManagerDatabaseServers>
15: </configuration>
And then you can access these values in code like so:
1: string devUrl = string.Empty;
2: var connectionManagerDatabaseServers = ConfigurationManager.GetSection("ConnectionManagerDatabaseServers") as NameValueCollection;
3: if (connectionManagerDatabaseServers != null)
4: {
5: devUrl = connectionManagerDatabaseServers["Dev"].ToString();
6: }
Sometimes though you don’t know what the keys are going
to be and you just want
to grab all of the values in that ConnectionManagerDatabaseServers section. In that case you can get them all like this:
1: // Grab the Environments listed in the App.config and add them
to our list.
2: var connectionManagerDatabaseServers = ConfigurationManager.GetSection("ConnectionManagerDatabaseServers") as NameValueCollection;
3: if (connectionManagerDatabaseServers != null)
4: {
5: foreach (var serverKey in connectionManagerDatabaseServers.AllKeys)
6: {
7: string serverValue = connectionManagerDatabaseServers.GetValues(serverKey).FirstOrDefault();
8: AddDatabaseServer(serverValue);
9: }
10: }
And here we just assume that the AddDatabaseServer() function adds the given string
to some list of strings. So this works great, but what about when we want
to bring in more values than just a single string (or technically you could use this
to bring in 2 strings, where the “key” could be the other string you want
to store; for example, we could have stored the value of the Key as the user-friendly name of the url).
More Advanced (and more complicated)
So if you want
to bring in more information than a string or two per object in the section, then you can no longer simply use the built-in System.Configuration.NameValueSectionHandler type provided for us. Instead you have
to build your own types. Here let’s assume that we again want
to configure a set of addresses (i.e. urls), but we want
to specify some extra info with them, such as the user-friendly name, if they require SSL or not, and a list of security groups that are allowed
to save changes made
to these endpoints.
So let’s start by looking at the app.config:
1: <?xml version="1.0" encoding="utf-8" ?>
2: <configuration>
3: <configSections>
4: <section name="ConnectionManagerDataSection" type="ConnectionManagerUpdater.Data.Configuration.ConnectionManagerDataSection, ConnectionManagerUpdater" />
5: </configSections>
6: <startup>
7: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
8: </startup>
9: <ConnectionManagerDataSection>
10: <ConnectionManagerEndpoints>
11: <add name="Development" address="Dev.MyDomain.
local" useSSL="false" />
12: <add name="Test" address="Test.MyDomain.
local" useSSL="true" />
13: <add name="Live" address="Prod.MyDomain.com" useSSL="true" securityGroupsAllowedToSaveChanges="ConnectionManagerUsers" />
14: </ConnectionManagerEndpoints>
15: </ConnectionManagerDataSection>
16: </configuration>
The first thing
to notice here is that my section is now using the type “ConnectionManagerUpdater.Data.Configuration.ConnectionManagerDataSection” (the fully qualified path
to my new class I created) “, ConnectionManagerUpdater” (the name of the assembly my new class is in). Next, you will also notice an extra layer down in the <ConnectionManagerDataSection> which is the <ConnectionManagerEndpoints> element. This is a new collection class that I created
to hold each of the Endpoint entries that are defined. Let’s look at that code now:
1: using System;
2: using System.Collections.Generic;
3: using System.Configuration;
4: using System.Linq;
5: using System.Text;
6: using System.Threading.Tasks;
7:
8: namespace ConnectionManagerUpdater.Data.Configuration
9: {
10: public class ConnectionManagerDataSection : ConfigurationSection
11: {
12: /// <summary>
13: /// The name of this section in the app.config.
14: /// </summary>
15: public const string SectionName = "ConnectionManagerDataSection";
16:
17: private const string EndpointCollectionName = "ConnectionManagerEndpoints";
18:
19: [ConfigurationProperty(EndpointCollectionName)]
20: [ConfigurationCollection(typeof(ConnectionManagerEndpointsCollection), AddItemName = "add")]
21: public ConnectionManagerEndpointsCollection ConnectionManagerEndpoints { get { return (ConnectionManagerEndpointsCollection)base[EndpointCollectionName]; } }
22: }
23:
24: public class ConnectionManagerEndpointsCollection : ConfigurationElementCollection
25: {
26: protected override ConfigurationElement CreateNewElement()
27: {
28: return new ConnectionManagerEndpointElement();
29: }
30:
31: protected override object GetElementKey(ConfigurationElement element)
32: {
33: return ((ConnectionManagerEndpointElement)element).Name;
34: }
35: }
36:
37: public class ConnectionManagerEndpointElement : ConfigurationElement
38: {
39: [ConfigurationProperty("name", IsRequired = true)]
40: public string Name
41: {
42: get { return (string)this["name"]; }
43: set { this["name"] = value; }
44: }
45:
46: [ConfigurationProperty("address", IsRequired = true)]
47: public string Address
48: {
49: get { return (string)this["address"]; }
50: set { this["address"] = value; }
51: }
52:
53: [ConfigurationProperty("useSSL", IsRequired = false, DefaultValue = false)]
54: public bool UseSSL
55: {
56: get { return (bool)this["useSSL"]; }
57: set { this["useSSL"] = value; }
58: }
59:
60: [ConfigurationProperty("securityGroupsAllowedToSaveChanges", IsRequired = false)]
61: public string SecurityGroupsAllowedToSaveChanges
62: {
63: get { return (string)this["securityGroupsAllowedToSaveChanges"]; }
64: set { this["securityGroupsAllowedToSaveChanges"] = value; }
65: }
66: }
67: }
So here the first class we declare is the one that appears in the <configSections> element of the app.config. It is ConnectionManagerDataSection and it inherits from the necessary System.Configuration.ConfigurationSection class. This class just has one property (other than the expected section name), that basically just says I have a Collection property, which is actually a ConnectionManagerEndpointsCollection, which is the next class defined.
The ConnectionManagerEndpointsCollection class inherits from ConfigurationElementCollection and overrides the requied fields. The first tells it what type of Element
to create when adding a new one (in our case a ConnectionManagerEndpointElement), and a function specifying what property on our ConnectionManagerEndpointElement class is the unique key, which I’ve specified
to be the Name field.
The last class defined is the actual meat of our elements. It inherits from ConfigurationElement and specifies the properties of the element (which can then be set in the xml of the App.config). The “ConfigurationProperty” attribute on each of the properties tells what we expect the name of the property
to correspond
to in each element in the app.config, as well as some additional information such as if that property is required and what it’s default value should be.
Finally, the code
to actually access these values would look like this:
1: // Grab the Environments listed in the App.config and add them
to our list.
2: var connectionManagerDataSection = ConfigurationManager.GetSection(ConnectionManagerDataSection.SectionName) as ConnectionManagerDataSection;
3: if (connectionManagerDataSection != null)
4: {
5: foreach (ConnectionManagerEndpointElement endpointElement in connectionManagerDataSection.ConnectionManagerEndpoints)
6: {
7: var endpoint = new ConnectionManagerEndpoint() { Name = endpointElement.Name, ServerInfo = new ConnectionManagerServerInfo() { Address = endpointElement.Address, UseSSL = endpointElement.UseSSL, SecurityGroupsAllowedToSaveChanges = endpointElement.SecurityGroupsAllowedToSaveChanges.Split(',').Where(e => !string.IsNullOrWhiteSpace(e)).ToList() } };
8: AddEndpoint(endpoint);
9: }
10: }
This looks very similar
to what we had before in the “simple” example. The main points of interest are that we cast the section as ConnectionManagerDataSection (which is the class we defined for our section) and then iterate over the endpoints collection using the ConnectionManagerEndpoints property we created in the ConnectionManagerDataSection class.
Also, some other helpful resources around using app.config that I found (and for parts that I didn’t really explain in this article) are:
How do you use sections in C# 4.0 app.config? (Stack Overflow) <== Shows how
to use Section Groups as well, which is something that I did not cover here, but might be of interest
to you.
How to: Create Custom Configuration Sections Using Configuration Section (MSDN)
ConfigurationSection Class (MSDN)
ConfigurationCollectionAttribute Class (MSDN)
ConfigurationElementCollection Class (MSDN)
I hope you find this helpful. Feel free
to leave a comment. Happy Coding!
