Global Static Dictionary Initialization from Database in Webapi - c#-4.0

Question

I want to Initialize a global Dictionary from Database in my web Api. Do i need to inject my DBContext in Global.Asax or Owin Startup. Any example would be much appreciated.

Answer 1

Any kind initialization purposes can be made in your custom defined OWIN Startup class class, like this:
using Microsoft.Owin;
using Microsoft.Owin.Security.OAuth;
using Owin;
using System;
[assembly: OwinStartup(typeof(WebAPIRestWithNest.Startup))]
namespace YourNamespace
{
public class Startup
{
public Dictionary<string, string> Table {get; private set;}
public void Configuration(IAppBuilder app)
{
// token generation
app.UseOAuthAuthorizationServer(new OAuthAuthorizationServerOptions
{
AllowInsecureHttp = false,
TokenEndpointPath = new PathString("/token"),
AccessTokenExpireTimeSpan = TimeSpan.FromHours(8),
Provider = new SimpleAuthorizationServerProvider()
});
// token consumption
app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());
app.UseWebApi(WebApiConfig.Register());
Table = ... Connect from DB and fill your table logic ...
}
}
}
After that you can use your Startup.Table property from your application.

Answer 2

In general, it is bad practice to access objects using static field in the asp.net applications because this may lead to bugs that are hardly detected and reproduced: especially this is true for non-immutable/not-thread-safe objects like Dictionary.
I assume you want to cache some DB data in memory to avoid excessive SQL queries. It is good idea to use standard asp.net caching for this purpose:
public IDictionary GetDict() {
var dict = HttpRuntime.Cache.Get("uniqueCacheKey") as IDictionary;
if (pvtData==null) {
dict = doLoadDictionaryFromDB(); // your code that loads data from DB
HttpRuntime.Cache.Add(cacheKey, dict,
null, Cache.NoAbsoluteExpiration,
new TimeSpan(0,5,0), // cache at least for 5 minutes after last access
CacheItemPriority.Normal, null);
}
return dict;
}
This approach allows you to select appropriate expiration policy (without the need to reinventing the wheel with static dictionary).
If you still want to use static dictionary, you can populate it on the application start (global.asax):
void Application_Start(object sender, EventArgs e)
{
// your code that initializes dictionary with data from DB
}