How to update multiple entries in bridge table using LINQ webapi C#

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C#

LINQ

WebAPI

ASP.NET4

, +

I have 4 tables in my database Users, Resources, Roles and a bridge table UserRoles.
I have written a PUT Request to update records in User and Resources table and along with it I have multiple entries against Users in UserRoles table which is a bridge table. So in UserRoles table I want to update RoleId against a particular user, how can I do that. I have tried so many methods but not able to update multiple entries in the bridge table. Any help is appreciated as I am new to this. I have to update entries in UserRoles table using LINQ. Here is the code below which I have written for that, please review: Thanks

What I have tried:

[HttpPut]
       public async Task<IHttpActionResult> UpdateUser(string id, [FromBody] dynamic body)
       {
           try
           {
               using (hospiceEntities db = new hospiceEntities())
               {
                   Guid guid_id = Guid.Parse(id);
                   var updateuser = db.Users.FirstOrDefault(e => e.Id == guid_id);
                   if (updateuser == null)
                   {
                       return Content(HttpStatusCode.NotFound, "User Not Found");
                   }
                   else
                   {
                       var query =
                       from resource in db.Resources
                       join user in db.Users on resource.UserId equals user.Id
                       from role in user.Roles
                       where resource.UserId == guid_id
                       select new
                       {
                           resource,
                           user,
                           role
                       };
                       foreach (var item in query)
                       {
                           item.user.PasswordQuestion = body.passwordquestion;
                           item.user.PasswordAnswer = body.passwordanswer;
                           item.resource.FirstName = body.firstname;
                           item.resource.LastName = body.lastname;
                           item.resource.MiddleName = body.middlename;
                           item.resource.Gender = body.gender;
                           item.resource.MaritalStatus = body.maritalstatus;
                           item.resource.Ethnicity = body.ethnicity;
                           item.resource.employmentType = body.employmenttype;
                        //   item.role.Id = updateuser.Roles.Add(body.roleId);

                           //deleteuser.Roles.Remove(item.Roles);
                           //updateuser.Roles.Add(body.roleId);
                       }
                       await db.SaveChangesAsync();
                   }
               }
               return Ok(Helper.SuccessResponse("User Updated"));
           }
           catch (Exception ex)
           {
               return BadRequest(ex.Message);
           }
       }