需要帮助使用 EF 从多个表中获取数据

Question

I am getting details in list format using this query, in that I am also getting user id.

reportProblemsList = objEntities.ReportProblems.ToList();

Now I want to get user details based on that user id from users table. So I have tried with foreach loop as per below.

foreach(var item in reportProblemsList)
{
   userdetails = objEntities.Users.Where(x => x.UserId == item.Userid).ToList();
}

Now I want to add this all userdetails in list and then access it. Below is my full code.

List<ReportProblem> reportProblemsList = new List<ReportProblem>();
List<User> userdetails = new List<User>();

reportProblemsList = objEntities.ReportProblems.ToList();

foreach(var item in reportProblemsList)
{
   userdetails = objEntities.Users.Where(x => x.UserId == item.Userid).ToList();
}

reportProblemsList.Add(userdetails);

But not able to get it working..any idea.

Thanks

Answer 1

I assume that you need a list users who reported the issue.

var userIds = objEntities.ReportProblems.Select(q=> q.Userid).ToList();
List<User> userdetails = objEntities.Users.Where(x => userIds.Contains( x.UserId)).ToList();

Answer 2

If you database is correctly designed from the given information, there is a high probability that your ReportProblem object has also the property User of type User . If this is the case you can instruct EF core to include such nested properties in your query by doing something like this:

var reportProblemsList = objEntities.ReportProblems
    .Include(report => report.User)
    .ToList();

If you don't have this property you have to create an anonymous type to hold the tuple:

var reportsWithUsers = objEntities.ReportProblems
    .Join(objEntities.Users, r => r.UserId, u => u.UserId, (Report, User) => (Report, User)
    .ToList();