passing a Dictionary<string, List<model>> model to a view

Question

Unclear on how to pass this model to my view. I have a list model being passed into my view. But I want to separate the Participant's inside the list depending on which User is logged in on the ViewBag.

current view code (working): this code works as it should but its not separating the participants depending on what user is logged in. it displays the entire list. I'm getting red squilies under @model, League inside my foreach line, and MMLeagueParticipants in my secondforeach. But it still worked.

error:

when I hovered over @model and League: The type or namespace name 'League' could not be found (are you missing a using directive or an assembly reference?)[LeagueProect]

When I hovered over MMLeagueParticipant: The type or namespace name 'MMLeagueParticpant' could not be found (are you missing a using directive or an assembly reference?`

---

//RED SQUIGLY #1 @model
@model List<League>
    @{    
        if (Model != null && Model.Any())
        {
            //RED SQUIGLY #2 League
            foreach(League i in Model)
            {
                //RED SQUIGLY #3 MMLeagueParticipant
                foreach (MMLeagueParticipant mmLeagueParticipant in i.allParticipants)
                {
                    <p>@mmLeagueParticipant.child.ParticipantFirstName @mmLeagueParticipant.child.ParticipantLastName</p>
                }  
            }
        }
        else
        {
            <p>the list is empty</p>
        }
    }

Attempt to separate (not working) still using @model List<League>. When I change my code to try and separate it crashes entirely

    <p>Your kid(s):</p>    
    if (Model != null && Model.Any())
    {
        foreach(League i in Model)
        {
            var userParticipants = i.allParticipants.Where(p => p?.child?.Parent?.UserId == ViewBag.UserId).ToList();
            foreach (MMLeagueParticipant mmLeagueParticipant in userParticipants)
            {
                <p>@mmLeagueParticipant.child.ParticipantFirstName @mmLeagueParticipant.child.ParticipantLastName</p>
            }  
        }
    }
    <p>not your kid(s):</p>
    if (Model != null && Model.Any())
    {
        foreach(League i in Model)
        {
            var userParticipants = i.allParticipants.Where(p => p?.child?.Parent?.UserId != ViewBag.UserId).ToList();
            foreach (MMLeagueParticipant mmLeagueParticipant in userParticipants)
            {
                <p>@mmLeagueParticipant.child.ParticipantFirstName @mmLeagueParticipant.child.ParticipantLastName</p>
            }  
        }
    }

The error I get from trying this:

NullReferenceException: Object reference not set to an instance of an object.

It doesn't like the lines:

• var userParticipants = i.allParticipants.Where(p => p.child.Parent.UserId == ViewBag.UserId).ToList();
• @await Html.PartialAsync("_Displayeach", Model["bbM7and8"])

I'm assuming the way I'm passing in the model to my view is incorrect. But entirely unsure why one way is working and the other isn't.

Controller details:

• in my controller I have a list of age groups that i add new participant models to.

• Then I pass the list to my RosterPageBasketball view.

• Inside that view I have 12 tabs; each displaying differnt lists depending on the age group.

• model used in RosterPageBacketball: @model List<League>

• Each tab in the RosterPageBasketball that displays different agegroups:

  @await Html.PartialAsync("_Displayeach", Model["bbM7and8"])

• _displayeach is my Current view code

The tabs were working as needed when showing all Participants with my Current view code (as showed above) with their own list of different age groups when I wasn't sperating the participants depending on if they belong to the logged on user or not.

each tab in my RosterPageBasketballcontains the following code: @await Html.PartialAsync("_Displayeach", Model["bbM#and#"])

where I thought the issue might be: ("_Displayeach", Model["bbM7and8"])

the model I'm sending to my partial is Model["bbM7and8"] but the model I'm using in my _Displayeach is @model List<League>. unsure how or if it's possible to pass in @model Dictionary<string, List<League>>.

---

controller:

public async Task<IActionResult> GetBasketballRoster()
{
    String[] leagueNames = new[]
    {
        "bbM7and8",
        "bbM9and10",
        "bbM11and12",
        "bbM13and14",
        "bbM15and16",
        "bbM17and18",
        "bbF7and8",
        "bbF9and10",
        "bbF11and12",
        "bbF13and14",
        "bbF15and16",
        "bbF17and18"
    };
        Dictionary<string, List<League>> d = new Dictionary<string, List<League>>();
        foreach (var name in leagueNames)
        {
            List<League> bbLeagues = await db.Leagues
            .Where(l => l.sport == "Basketball")
            .Where(l => l.ageRange==name)
            .ToListAsync();

            foreach (League league in bbLeagues)
            {
                List<MMLeagueParticipant> leagueParticipants = await db.Entry(league)
                    .Collection(l => l.allParticipants)
                    .Query() // <-- This is needed to allow for `Include()`
                    .Include(mmp => mmp.child)
                    .ToListAsync();
            }
            d.Add(name,bbLeagues);
        }
        return View("RosterPageBasketball", d);
}

• Dictionary<string, List> d is passed to the RosterpageBasketball
• _Displayeach view is passes a model["bbM#and#"]
• _Displayeach view uses @model List<League>

Answer 1

From your code, it seems you want to display List<League> which is in partial view for specific ageRange.

Here is a working demo you could follow:

Model:

public class League
{
    public string sport { get; set; }
    public string ageRange { get; set; }
    public List<MMLeagueParticipant> allParticipants { get; set; }
}
public class MMLeagueParticipant
{
    public child child { get; set; }
}
public class child
{
    public string ParticipantFirstName { get; set; }
    public string ParticipantLastName { get; set; }
}

RosterPageBasketball.cshtml:

@model Dictionary<string, List<League>>

@{ 
    var data = Model.Where(a => a.Key == "bbF17and18").Select(a => a.Value).FirstOrDefault();
}
@await Html.PartialAsync("_Displayeach", data)

_Displayeach.cshtml:

@model List<League>
@{
    if (Model != null && Model.Any())
    {
        foreach (League i in Model)
        {
            foreach (MMLeagueParticipant mmLeagueParticipant in i.allParticipants)
            {
                <p>@mmLeagueParticipant.child.ParticipantFirstName @mmLeagueParticipant.child.ParticipantLastName</p>
            }
        }
    }
    else
    {
        <p>the list is empty</p>
    }
}

Controller:

public async Task<IActionResult> Index()
{
    String[] leagueNames = new[]
    {
        "bbM7and8",
        "bbM9and10",
        "bbM11and12",
        "bbM13and14",
        "bbM15and16",
        "bbM17and18",
        "bbF7and8",
        "bbF9and10",
        "bbF11and12",
        "bbF13and14",
        "bbF15and16",
        "bbF17and18"
    };
    Dictionary<string, List<League>> d = new Dictionary<string, List<League>>();
    foreach (var name in leagueNames)
    {
        //hard coded the data....
        List<League> bbLeagues = new List<League>()
        {
            new League(){sport="Basketball",ageRange="bbF17and18",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="San",ParticipantLastName="Da" } } } },
            new League(){sport="Basketball",ageRange="bbF17and18",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="Api",ParticipantLastName="Ee" } } }},
            new League(){sport="Basketball",ageRange="bbF9and10",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="May",ParticipantLastName="Fa" } } }},
            new League(){sport="Basketball",ageRange="bbM17and18",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="Ben",ParticipantLastName="He" } } }},
            new League(){sport="Basketball",ageRange="bbF15and16",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="Jun",ParticipantLastName="Pa" } } }},
            new League(){sport="FootBall",ageRange="bbF15and16",allParticipants =new List<MMLeagueParticipant>(){ new MMLeagueParticipant() { child= new child() {ParticipantFirstName="Pen",ParticipantLastName="Me" } } }}
        };

        var data = bbLeagues.Where(l => l.sport == "Basketball").Where(l => l.ageRange == name).ToList();
        d.Add(name, data);
    }
    return View("Index", d);
}