create secure api using oauth in csharp

main.cs
Install-Package Microsoft.AspNet.WebApi.Owin
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main.cs
using Microsoft.Owin;
using Microsoft.Owin.Security.OAuth;
using Owin;
using System;
using System.Web.Http;

[assembly: OwinStartup(typeof(YourProject.Startup))]

namespace YourProject
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            HttpConfiguration config = new HttpConfiguration();

            ConfigureOAuth(app);

            WebApiConfig.Register(config);

            app.UseWebApi(config);
        }

        public void ConfigureOAuth(IAppBuilder app)
        {
            OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
            {
                AllowInsecureHttp = false,
                TokenEndpointPath = new PathString("/token"),
                AccessTokenExpireTimeSpan = TimeSpan.FromMinutes(30),
                Provider = new OAuthProvider()
            };

            app.UseOAuthAuthorizationServer(OAuthServerOptions);
            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());
        }
    }

    public class OAuthProvider : OAuthAuthorizationServerProvider
    {
        public override Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
        {
            context.Validated();
            return Task.FromResult<object>(null);
        }

        public override Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            // Your authentication logic goes here
            if (context.UserName == "your_username" && context.Password == "your_password")
            {
                ClaimsIdentity oAuthIdentity = new ClaimsIdentity(context.Options.AuthenticationType);
                oAuthIdentity.AddClaim(new Claim(ClaimTypes.Name, context.UserName));
                oAuthIdentity.AddClaim(new Claim(ClaimTypes.Role, "user"));

                context.Validated(oAuthIdentity);
            }
            else
            {
                context.SetError("invalid_grant", "The user name or password is incorrect.");
            }

            return Task.FromResult<object>(null);
        }
    }
}
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main.cs
[Authorize]
public class MySecureController : ApiController
{
    // Your secured API endpoints go here
}
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