C# 你不必实施它。因为它都是模板的一部分。您所要做的就是添加声明，并将Users表添加到业务上下文中。感谢您提供了非常全面的答案。我将开始实施它。一旦我成功了（可能需要一段时间），我一定会让你知道。如果你创建了一个新的Asp.NETMVC项目，你就不必实现它。

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你不必实施它。因为它都是模板的一部分。您所要做的就是添加声明，并将Users表添加到业务上下文中。感谢您提供了非常全面的答案。我将开始实施它。一旦我成功了（可能需要一段时间），我一定会让你知道。如果你创建了一个新的Asp.NETMVC项目，你就不必实现它。因为它都是模板的一部分。您所要做的就是添加声明，并将Users表添加到业务上下文中。

public ActionResult Index(int? id, int? csearchid)
        {
            var companies = db.Companies
              .OrderBy(i => i.CompanyName)
              .Where(t => t.UserName == User.Identity.Name);
        return View(companies);

public class Company
{
    public int CompanyID { get; set; }

    // Link naar de Userid in Identity: AspNetUsers.Id
    [Display(Name = "Username")]
    public string UserName { get; set; }        
    public string CompanyName { get; set;}
    public string CompanyContactName { get; set; }
    [DataType(DataType.EmailAddress)]        
    public string CompanyEmail { get; set; }
    public string CompanyPhone { get; set; }        

    [Timestamp]
    public byte[] RowVersion { get; set; }

    //One to Many Navigatie links
    public virtual ICollection<Csearch> Csearches { get; set; }

var companies = from c in db.Companies join u in db.AspNetUsers
                on c.UserId equals u.UserId
                orderby c.CompanyName
                where u.UserName = User.Identity.Name 
                select c;

select new { Company = c, User = u.UserName };

public class Company
{
    public int CompanyID { get; set; }

    // Link naar de Userid in Identity: AspNetUsers.Id
    // [Display(Name = "Username")] <-- Get rid of these
    // public string UserName { get; set; } <-- get rid of these
...
}

public class ApplicationUser : IdentityUser
{
    public int CompanyId { get; set; }
}

var companies = from c in db.Companies join u in db.AspNetUsers
            on c.CompanyId equals u.CompanyId // <-- Change to this
            orderby c.CompanyName
            where u.UserName = User.Identity.Name 
            select c;

userManager.AddClaim(id, new Claim("UserId", UserId));

public class ApplicationUser : IdentityUser
{
    public int UserId { get; set; }

    public string DisplayUserName { get; set; }

    public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
    {
        // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);

        // Add custom user claims here
        userIdentity.AddClaim(new Claim("UserId", UserId));
        userIdentity.AddClaim(new Claim("DisplayUserName", DisplayUserName));

        return userIdentity;
    }
}

var user = (System.Security.Claims.ClaimsIdentity)User.Identity;
var userId = user.FindFirstValue("UserId");