让所有用户都扮演角色时出错

Question

I'm trying to get a list of all users in a role, and despite the numerous questions and links I've read on here, I can't seem to figure this Identity stuff out. Below is what I'm currently working with:

IdentityRole role = context.Roles.Where(x => x.Name == rolesDDL.SelectedValue).First();
var users = context.Users.Where(x => x.Roles.Any(r => r.RoleId == role.Id));

However this gets an error that says "Sequence contains no elements" on the role line. I tried doing a similar bit of code with the UserManager/RoleManager but that had the same result:

var userManager = Request.GetOwinContext().GetUserManager<ApplicationUserManager>();
var roleManager = Request.GetOwinContext().GetUserManager<ApplicationRoleManager>();

IdentityRole role = roleManager.Roles.Where(x => x.Name == rolesDDL.SelectedValue).First();
var users = userManager.Users.Where(x => x.Roles.Any(r => r.RoleId == role.Id));

EDIT: It seems to be an issue with the RoleManager not being able to actually find my roles. If I go into ServerExplorer I can see the roles in my AspNetRoles table but after instantiating my RoleManager from the OWIN context it doesn't seem to have any roles still. Could this be an issue from installing RavenDB for the data? I saw how to migrate users to Raven also but I was hoping to get it working with defaults first, before I made more issues for myself.

This is what I currently have in this function:

var userManager = Request.GetOwinContext().GetUserManager<ApplicationUserManager>();
var roleManager = Request.GetOwinContext().GetUserManager<ApplicationRoleManager>();

//IdentityRole role = roleManager.Roles.Where(x => x.Name == rolesDDL.SelectedValue).First();
//var users = userManager.Users.Where(x => x.Roles.Any(r => r.RoleId == role. 

//IdentityRole role = context.Roles.Where(x => x.Name == rolesDDL.SelectedValue).First();
//var users = context.Users.Where(x => x.Roles.Any(r => r.RoleId == role.Id));

var users = roleManager.FindByName(rolesDDL.SelectedItem.Text).Users;

EDIT: Adding initializers per request, found in startup.auth.cs:

app.CreatePerOwinContext(ApplicationDbContext.Create);
app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);
app.CreatePerOwinContext<ApplicationRoleManager>(ApplicationRoleManager.Create);

Answer 1

If you use your roleManager instead and filter it with the role name rather than the role id you can use the following:

var roleManager = HttpContext.Current
        .GetOwinContext()
        .Get<ApplicationRoleManager>();

var roleName = rolesDDL.SelectedItem.Text;
var users = roleManager.FindByName(roleName).Users