The simplest way is an anonymous method passed into Label.Invoke
:
// Running on the worker thread
string newText = "abc";
form.Label.Invoke((MethodInvoker)delegate {
// Running on the UI thread
form.Label.Text = newText;
});
// Back on the worker thread
Notice that Invoke
blocks execution until it completes--this is synchronous code. The question doesn't ask about asynchronous code, but there is lots of content on Stack Overflow about writing asynchronous code when you want to learn about it.
Here's how I do it.
I decided to use IPrincipal instead of IIdentity because it means I don't have to implement both IIdentity and IPrincipal.
Create the interface
interface ICustomPrincipal : IPrincipal
{
int Id { get; set; }
string FirstName { get; set; }
string LastName { get; set; }
}
CustomPrincipal
public class CustomPrincipal : ICustomPrincipal
{
public IIdentity Identity { get; private set; }
public bool IsInRole(string role) { return false; }
public CustomPrincipal(string email)
{
this.Identity = new GenericIdentity(email);
}
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
CustomPrincipalSerializeModel - for serializing custom information into userdata field in FormsAuthenticationTicket object.
public class CustomPrincipalSerializeModel
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
LogIn method - setting up a cookie with custom information
if (Membership.ValidateUser(viewModel.Email, viewModel.Password))
{
var user = userRepository.Users.Where(u => u.Email == viewModel.Email).First();
CustomPrincipalSerializeModel serializeModel = new CustomPrincipalSerializeModel();
serializeModel.Id = user.Id;
serializeModel.FirstName = user.FirstName;
serializeModel.LastName = user.LastName;
JavaScriptSerializer serializer = new JavaScriptSerializer();
string userData = serializer.Serialize(serializeModel);
FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket(
1,
viewModel.Email,
DateTime.Now,
DateTime.Now.AddMinutes(15),
false,
userData);
string encTicket = FormsAuthentication.Encrypt(authTicket);
HttpCookie faCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket);
Response.Cookies.Add(faCookie);
return RedirectToAction("Index", "Home");
}
Global.asax.cs - Reading cookie and replacing HttpContext.User object, this is done by overriding PostAuthenticateRequest
protected void Application_PostAuthenticateRequest(Object sender, EventArgs e)
{
HttpCookie authCookie = Request.Cookies[FormsAuthentication.FormsCookieName];
if (authCookie != null)
{
FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(authCookie.Value);
JavaScriptSerializer serializer = new JavaScriptSerializer();
CustomPrincipalSerializeModel serializeModel = serializer.Deserialize<CustomPrincipalSerializeModel>(authTicket.UserData);
CustomPrincipal newUser = new CustomPrincipal(authTicket.Name);
newUser.Id = serializeModel.Id;
newUser.FirstName = serializeModel.FirstName;
newUser.LastName = serializeModel.LastName;
HttpContext.Current.User = newUser;
}
}
Access in Razor views
@((User as CustomPrincipal).Id)
@((User as CustomPrincipal).FirstName)
@((User as CustomPrincipal).LastName)
and in code:
(User as CustomPrincipal).Id
(User as CustomPrincipal).FirstName
(User as CustomPrincipal).LastName
I think the code is self-explanatory. If it isn't, let me know.
Additionally to make the access even easier you can create a base controller and override the returned User object (HttpContext.User):
public class BaseController : Controller
{
protected virtual new CustomPrincipal User
{
get { return HttpContext.User as CustomPrincipal; }
}
}
and then, for each controller:
public class AccountController : BaseController
{
// ...
}
which will allow you to access custom fields in code like this:
User.Id
User.FirstName
User.LastName
But this will not work inside views. For that you would need to create a custom WebViewPage implementation:
public abstract class BaseViewPage : WebViewPage
{
public virtual new CustomPrincipal User
{
get { return base.User as CustomPrincipal; }
}
}
public abstract class BaseViewPage<TModel> : WebViewPage<TModel>
{
public virtual new CustomPrincipal User
{
get { return base.User as CustomPrincipal; }
}
}
Make it a default page type in Views/web.config:
<pages pageBaseType="Your.Namespace.BaseViewPage">
<namespaces>
<add namespace="System.Web.Mvc" />
<add namespace="System.Web.Mvc.Ajax" />
<add namespace="System.Web.Mvc.Html" />
<add namespace="System.Web.Routing" />
</namespaces>
</pages>
and in views, you can access it like this:
@User.FirstName
@User.LastName
Best Answer
I've found a solution to this problem.
Basically I add claim with admin username, if this claim exists, I know that impersonation is happening. When admin wants to stop impersonation, system retrieves original username for the claims, deletes old impersonated-cookie and creates a new cookie for the admin:
More information is in my blog-post: User impersonation with ASP.Net Identity 2.
User Impersonation in Asp.Net Core
Upd July 2017: this topic is quite popular, so I've looked into user impersonation in Core and principles are very similar with updated API. Here is how to impersonate:
This is how to stop impersonation:
Full explanation in my blog: http://tech.trailmax.info/2017/07/user-impersonation-in-asp-net-core/ Full code sample on GitHub: https://github.com/trailmax/AspNetCoreImpersonation