C# AppSettings array

Question

I have some string constants that I need to access from multiple files. Since the values of these constants might change from time to time, I decided to put them in AppSettings rather than a constants class so that I don't have to recompile every time I change a constant.

Sometimes I need to work with the individual strings and sometimes I need to work with all of them at once. I'd like to do something like this:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <appSettings>
        <add key="CONST1" value="Hi, I'm the first constant." />
        <add key="CONST2" value="I'm the second." />
        <add key="CONST3" value="And I'm the third." />

        <add key="CONST_ARR" value=[CONST1, CONST2, CONST3] />
    </appSettings>
</configuration>

The reasoning being that I'll then be able to do stuff like

public Dictionary<string, List<double>> GetData(){
    var ret = new Dictionary<string, List<double>>();
    foreach(string key in ConfigurationManager.AppSettings["CONST_ARR"])
        ret.Add(key, foo(key));
    return ret;
}

//...

Dictionary<string, List<double>> dataset = GetData();

public void ProcessData1(){
    List<double> data = dataset[ConfigurationManager.AppSettings["CONST1"]];
    //...
}

Is there a way to do this? I'm pretty new to this and I concede that this might be horrendous design.

Answer 1

You do not need to put array of key in AppSettings key as you can iterate all keys of AppSetting from code itself. So, your AppSettings should be like this :

 <appSettings>
    <add key="CONST1" value="Hi, I'm the first constant." />
    <add key="CONST2" value="I'm the second." />
    <add key="CONST3" value="And I'm the third." />
</appSettings>

After this, you can create global static dictionary which you can access from all part of the program :

public static Dictionary<string, List<double>> Dataset
{
       get
       {
            var ret = new Dictionary<string, List<double>>();
            // Iterate through each key of AppSettings
            foreach (string key in ConfigurationManager.AppSettings.AllKeys)
                ret.Add(key, Foo(ConfigurationManager.AppSettings[key]));
            eturn ret;
        }
}

As Foo method has been accessed from static property, you need to define Foo method as static method. so, your Foo method should look like this :

private static List<double> Foo(string key)
{
    // Process and return value 
    return Enumerable.Empty<double>().ToList(); // returning empty collection for demo
}

Now, you can access Dataset dictionary by its key in following way :

public void ProcessData1()
{
    List<double> data = Dataset["CONST1"];
    //...
}