无法为此找到正确的linq查询

Question

I want to generate a list in my datagrid view box. I have the userId, uId , and i want to at first search for the user in the database using the id and then display the user's corresponding username and rolename. How can i do this? Below, i've attempted to search for user using UserId, but since i'm new to this i know that the rest of the code after brackets isn't right. I could use some help with the syntax. Thanks

var list = _db.AspNetUserRoles.FirstOrDefault(w => w.UserId == uId)
            {
                w.AspNetUser.UserName,
                w.AspNetRole.Name
            });

            dataGridView1.DataSource = list;

Answer 1

Use the Where clause instead of FirstOrDefault , because FirstOrDefault returns the first element of a sequence. After the Where clause use Select to make a anonymous class with UserName and Name properties:

var list = _db.AspNetUserRoles.Where(w => w.UserId == uId).Select(w => new
            {
                UserName = w.AspNetUser.UserName,
                Name = w.AspNetRole.Name
            }).ToList();

dataGridView1.DataSource = list;

Answer 2

As lan Mercer said FirstOrDefault returns first or default (single) value, if you want list of elements which satisfies condition provided by you then use where .

var list = _db.AspNetUserRoles.Where(w => w.UserId == uId)
            {
                Uname = w.AspNetUser.UserName,
                Name = w.AspNetRole.Name
            });

            dataGridView1.DataSource = list;