How to Efficiently Retrieve Users and Their Associated Roles in .NET Core 2.1?

Retrieving Users and Associated Roles in .NET Core 2.1

In managing users and their roles, it's crucial to have a mechanism for retrieving both efficiently. This article delves into how to accomplish this task in .NET Core 2.1 using the Identity Framework.

Initial Attempts and Issues

One common approach involves modifying the ApplicationUser class to include a Roles property. However, this is no longer supported in .NET Core. Attempts to use this implementation will result in an error when trying to include roles in the query.

Implementing a Custom Relationship Table

To overcome this issue, a custom relationship table is required. This table will connect the ApplicationUser and IdentityRole tables, allowing us to retrieve users and their associated roles.

The following entities define this relationship:

• ApplicationUser: Represents the application user.
• ApplicationUserRole: Links users to roles.
• ApplicationRole: Represents the application role.

Configuring the DbContext

The ApplicationDbContext must be updated to handle these entities and their relationships:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser, ApplicationRole, string>
{
    protected override void OnModelCreating(ModelBuilder builder)
    {
        // Define the relationship between ApplicationUser and ApplicationUserRole
        builder.Entity<ApplicationUserRole>()
            .HasKey(ur => new { ur.UserId, ur.RoleId });
        builder.Entity<ApplicationUserRole>()
            .HasOne(ur => ur.User)
            .WithMany(u => u.UserRoles)
            .HasForeignKey(ur => ur.UserId)
            .IsRequired();
        builder.Entity<ApplicationUserRole>()
            .HasOne(ur => ur.Role)
            .WithMany(r => r.UserRoles)
            .HasForeignKey(ur => ur.RoleId)
            .IsRequired();
    }
}

Eager Loading in the Razor Page

To retrieve users and their associated roles, the following code is added to the Razor Page:

public IActionResult OnGetAsync()
{
    this.Users = userManager.Users
        .Include(u => u.UserRoles)
        .ThenInclude(ur => ur.Role)
        .ToList();
    return Page();
}

The ".Include(u => u.UserRoles)" part eagerly loads the UserRoles for each user. The ".ThenInclude(ur => ur.Role)" part further eagerly loads the Role for each UserRole. This ensures that both users and their roles are available in the model.

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