Using Enums in C#

I have a Windows Application that is accepting a string via command line parameter.

The string is going to be one of the following: 19, 20, 21, 23, 25. This is an ID that is used to build a URL dynamically.

I've used enums in plenty of apps before, but I've never actually built an enum from scratch so (I feel foolish saying this), I don't entirely understand them.

Based on the string that's passed in, I want to set a UI label. The corresponding val开发者_StackOverflow社区ues I want to display are as follows (recall the # value is the string that's passed in):

19 = Facebook
20 = Twitter
21 = YouTube
23 = Flickr
25 = Blogs

So if 23 is passed in, my label would say "Flickr". Is this something I can do with enums?

public Form1(string collectorID)
{
    InitializeComponent();
    this.CollectorID = collectorID;
    labelCollector.Text = // Set label here
    WebConnection.Create(CollectorID);
}

Thanks!

Scott

You could do this with enums, but you probably shouldn't. Values of a enum are meant to be used in code, not displayed to users. What happens if you want to display “Foo-Bar Service”?

Because of this and because it seems you actually just want a mapping between numbers and strings, you should do just that: use Dictionary<int, string> or a switch.

Yes you can. Have a look at MSDN: enum

It doesn't sound like something that should be done with an enum, but if thats your solution you can set your enum as:

public enum MyEnum
{
    Facebook = 19,
    Twitter = 20
    .
    .
}

Edit:

To get the value name:

string s = Enum.GetName(typeof (MyEnum), 19);

enum Sites
{
    Facebook = 19,
    Twitter = 20,
    YouTube = 21,
    Flickr = 23,
    Blogs = 25,
}

//

int i = 19;

if (!Enum.IsDefined(typeof(Sites), i))
{
    throw new Exception();
}

string str = ((Sites)i).ToString();

Be aware that many programmers (including me) consider using the ToString() of an enum a little "foolish" (this because you are making everything "immutable unless you modify the program" and "unlocalizable")

I'll add that you could do it with a Dictionary (a little better, the Dictionary could be loaded dynamically):

Dictionary<int, string> sites = new Dictionary<int, string>() 
{
    { 19, "Facebook" },
    { 20, "Twitter" },
    { 21, "YouTube" },
    { 23, "Flickr" }, 
    { 25, "Blogs" },
};

//

string str2;

if (!sites.TryGetValue(i, out str2))
{
    throw new Exception();
}

// str2 contains your site description

public enum MyEnum
{
    Facebook = 19,
    Twitter = 20,
    YouTube = 21,
    Flickr = 23,
    Blogs = 25,
}

public Form1(MyEnum collectorID)
{
    InitializeComponent();
    this.CollectorID = collectorID;
    labelCollector.Text = collectorId.toString();
    WebConnection.Create(CollectorID);
}

Use it in following way:

public enum UrlType
{
    Facebook = 19,
    Twitter = 20,
    YouTube = 21,
    Flickr = 23,
    Blogs = 25
}

    public string ParseUrlType(string type)
    {
        int urlTypeId = Convert.ToInt32(type);
        if (!Enum.IsDefined(typeof(UrlType), urlTypeId))
            return null;

        UrlType urlType = (UrlType)urlTypeId;
        return urlType.ToString();
    }

Use Enum.IsDefined to filter out invalid input and store names in a dictionary.

public enum SocialNetwork {
    Facebook = 19,
    Twitter = 20,
    YouTube = 21,
    Flickr = 23,
    Blogs = 25
}

var names = new Dictionary<SocialNetwork, String>() {
    { SocialNetwork.Facebook, "Facebook"}
    ...
};


String input = /*Read user input*/;
Int32 socialNetworkInteger;
if (Int32.TryParse(input, out socialNetworkInteger)) {
    if (Enum.IsDefined(typeof(SocialNetwork), socialNetworkInteger)) {
        String nameToDisplay = names[(SocialNetwork) socialNetworkInteger];
    }
}