使用ASP Identity的UserManager时，如何关联其他实体？

下面提供几种可行的替代方案：

方案1：直接通过DbContext查询（最直观） #

既然UserManager底层依赖DbContext，直接操作上下文结合角色关联查询，同时Include需要的导航属性即可：

// 获取Member角色用户并关联Projects、School
var members = await _context.Users
    .Include(u => u.Projects)
    .Include(u => u.School)
    .Where(u => u.Roles.Any(r => r.Role.Name == "Member"))
    .ToListAsync();

// 获取Leader角色用户并关联Projects、School
var leaders = await _context.Users
    .Include(u => u.Projects)
    .Include(u => u.School)
    .Where(u => u.Roles.Any(r => r.Role.Name == "Leader"))
    .ToListAsync();

注：如果你的角色关联是通过IdentityUserRole<TKey>，需确保上下文已正确配置角色导航属性，否则可能需要显式关联Roles表。

方案2：扩展UserManager添加带Include的方法 #

要是想继续沿用UserManager的封装逻辑，可以给它扩展一个支持Include的方法：

public static class UserManagerExtensions
{
    public static async Task<IList<AppUser>> GetUsersInRoleWithIncludesAsync(
        this UserManager<AppUser> userManager,
        string roleName,
        params Expression<Func<AppUser, object>>[] includes)
    {
        var targetRole = await userManager.FindByNameAsync(roleName);
        if (targetRole == null)
            return new List<AppUser>();

        var userQuery = userManager.Users
            .Where(u => u.Roles.Any(r => r.RoleId == targetRole.Id));

        // 批量添加Include
        foreach (var includeExpr in includes)
        {
            userQuery = userQuery.Include(includeExpr);
        }

        return await userQuery.ToListAsync();
    }
}

使用时直接调用扩展方法：

var members = await _userManager.GetUsersInRoleWithIncludesAsync(
    "Member", 
    u => u.Projects, 
    u => u.School);

方案3：利用UserManager.Users属性构建查询 #

UserManager本身暴露了Users属性（IQueryable类型），可以直接基于它构建带Include的查询：

var memberRole = await _userManager.FindByNameAsync("Member");
var members = await _userManager.Users
    .Include(u => u.Projects)
    .Include(u => u.School)
    .Where(u => u.Roles.Any(r => r.RoleId == memberRole.Id))
    .ToListAsync();

内容的提问来源于stack exchange，提问作者Feldmarshall