1. You are using .NET Framework v4.5 for all you projects
2. You are using WebMatrix.WebData.SimpleMembershipProvider as your MembershipProvider in your WebApi project.
   To enable this, your web.config must have the following entries:
   
	<system.web>
		<compilation debug="true" targetFramework="4.5"/>
		<roleManager enabled="true" defaultProvider="SimpleRoleProvider">
			<providers>
				<clear />
				<add name="SimpleRoleProvider" type="WebMatrix.WebData.SimpleRoleProvider, WebMatrix.WebData" />
			</providers>
		</roleManager>
		<membership defaultProvider="SimpleMembershipProvider">
			<providers>
				<clear />
				<add name="SimpleMembershipProvider" type="WebMatrix.WebData.SimpleMembershipProvider, WebMatrix.WebData" />
			</providers>
		</membership>
	<sytem.web>
3. You have a connection strings as shown below:
	<connectionStrings>
		<add name="DefaultConnection" connectionString="Your SQL connection string" providerName="System.Data.SqlClient" />
		<add name="StorageConnectionString" connectionString="DefaultEndpointsProtocol=https;AccountName=Your azure storage account name;AccountKey=Your Azure storage account key" />
	</connectionStrings>
 4. You have the following appsettings in web.config:
	<appSettings>
        <!-- The below value gives the name of the connection string configured earlier -->
        <add key="OAuth2ConnectionStringName" value="StorageConnectionString" />
        <!-- If set to true, the below key will ensure that calls to your API come over SSL. Set to true on production systems -->
        <add key="OAuth2RequireSsl" value="False"/>
   </appSettings>
5. Make sure that the following DOES NOT EXIST in your web.config:
	<dependentAssembly>
		<assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
		<bindingRedirect oldVersion="0.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
	</dependentAssembly>
6. Follow the FAQ below for more details:

<system.webServer>
	<modules runAllManagedModulesForAllRequests="true">
		<remove name="WebDAVModule" />
	</modules>
    <handlers>
		<remove name="WebDAV" />
	</handlers>
</system.webServer>

	public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
			//Since our handler uses WebSecurity, we initialize it here, otherwise it may cause errors in it is accessed before it is initialized
		    try
            {
                WebSecurity.InitializeDatabaseConnection("DefaultConnection", "UserProfile", "UserId", "UserName", autoCreateTables: true);
            }
            catch(Exception)
            {
            }
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional },
                constraints: null,
                handler: HttpClientFactory.CreatePipeline(
                          new HttpControllerDispatcher(config),
                          new DelegatingHandler[] { new OAuth2ClientCredentialsHandler() })
            );

            //Use the below lines to return JSON from your API instead of the default XML
            var appXmlType = config.Formatters.XmlFormatter.SupportedMediaTypes.FirstOrDefault(t => t.MediaType == "application/xml");
            config.Formatters.XmlFormatter.SupportedMediaTypes.Remove(appXmlType);
        }
    }

<configuration>
    <connectionStrings>
        <add name="StorageConnectionString" connectionString="DefaultEndpointsProtocol=https;AccountName=your_account;AccountKey=your_key" />
    </connectionStrings>
    <appSettings>
        <!-- The below value gives the name of the connection string configured earlier -->
        <add key="OAuth2ConnectionStringName" value="StorageConnectionString" />
        <!-- If set to true, the below key will ensure that calls to your API come over SSL -->
        <add key="OAuth2RequireSsl" value="False"/>
   </appSettings>
</configuration>

OAuth2DataFactory.CredentialManager.CreateCredential(string username, Dictionary<string, string> properties);

//Retrieve a credential based on consumer secret and consumer key. The credential object will contain the properties used while creating the credential.
OAuth2DataFactory.CredentialManager.GetCredential(string consumer_Key, string consumer_Secret);

//Retrieve all the credentials for a particular user (a user can have multiple consumer key/consumer secret pairs which can be deleted if any of them
//is compromised)
OAuth2DataFactory.CredentialManager.GetCredentials(string username);

//Delete a compromised credential
OAuth2DataFactory.CredentialManager.DeleteCredential(string consumer_Key, string consumer_Secret);

OAuth2DataFactory.CredentialManager.SetProperties(string consumer_Key, string consumer_Secret, Dictionary<string, string> properties);

Thread.CurrentPrincipal.Identity.Name in your WebAPI methods to find the username for the user accessing your API.

string consumerKey = (string) Request.Properties["ConsumerKey"];
string consumerSecret = (string) Request.Properties["ConsumerSecret"];
OAuth2Credential credential = OAuth2ClientCredentialsGrant.OAuth2DataFactory.CredentialManager.GetCredential(consumerKey, consumerSecret);

The credential object thus retrieved will have the properties. If a property changes, you can change it in the object and persist it back to the store using:
OAuth2DataFactory.CredentialManager.SetProperties(consumerKey , consumerSecret , credential.Properties);