Asp.net – How to pass a parameter from one partial view to another

I have a partial view of users with a shop details page. I have added a partial modal to mark users as sickness. This is my partial view of the users:

@model Shop

<div class="mb-3 d-flex border-bottom align-items-center justify-content-between">
    <h3 class="text-secondary">Employees in @Model.Name</h3>

    <a [email protected]("admin") asp-controller="User" asp-action="Register" asp-route-id="@Model.Id"
        class="btn-add-employee" title="Add a new user"><i class="bi bi-person-fill-add" ></i></a>

</div>

<table class="table table-sm">
    <thead>
        <tr>
            <th>Name</th>
            <th>Surname</th>
            <th>Role</th>
            <th>Edit Clock In-Out and Add Holiday Leave</th>
            <th>Sickness</th>
            <th></th>
        </tr>
    </thead>
    <tbody>
        @if (Model.Users.Count == 0)
        {
            <tr>
                <td colspan="4">No Employees...</td>
            </tr>
        }
        else
        {
            @foreach (var u in Model.Users)
            {
                
                var rowClass = "table-danger"; // Default to red

                 // Get today's timecard for the user
                 var todayTimeCard = u.TimeCards.Where(tc => tc.ClockIn.Date == DateTime.Today).OrderByDescending(tc => tc.ClockIn).FirstOrDefault();

                    if (todayTimeCard != null)
                    {
                        if (todayTimeCard.Holiday)
                        {
                            rowClass = "table-primary"; // Blue row for holiday
                        }
                        else if (todayTimeCard.Sickness)
                        {
                            rowClass = "table-warning"; // Yellow row for sickness
                        }
                        else
                        {
                            rowClass = "table-success"; // Green row for regular time card
                        }
                    }
              

                <tr class="@rowClass">
                    <td>@u.Name</td>
                    <td>@u.LastName</td>
                    <td>@u.Role</td>
                    <td>@u.ShopId</td>
                    <td> <a [email protected]("manager,admin") asp-controller="User" asp-action="TimeCardLog" asp-route-id="@u.Id"
                            class="btn"><i class="bi bi-pencil-fill"></i></a>
                    </td>
                    <td>
                          @{ViewBag.UserId = u.Id;}
                          <button [email protected]("manager,admin") data-bs-toggle="modal" data-bs-target="#AddSicknessTimeCardModal"
                    class="btn btn-sm btn-outline-warning"><i class="bi bi-emoji-frown" title="mark as sick"></i>Mark as Sick</button>
                    </td>

                    <td class="text-end">

                        <a [email protected]("admin") asp-controller="User" asp-action="Edit" asp-route-id="@u.Id"
                            class="btn btn-sm btn-outline-dark">Edit employee details</a>
                        <br>

                        <a [email protected]("admin") asp-controller="User" asp-action="Delete" asp-route-id="@u.Id"
                            class="buttondelete btn-sm btn-outline-danger">
                            <i class="bi bi-trash" title="Delete User"></i>Remove employee</a>
                        <br>

                        <a [email protected]("admin") asp-controller="User" asp-action="ReassignShop" asp-route-id="@u.Id"
                            class="buttondelete btn-sm btn-outline-danger">
                            <i class="bi bi-arrow-right" title="Reassign User"></i>Re-assign employee</a>

                    </td>
                   
                </tr>
            }
        }
    </tbody>
</table>



<!-- Mark as sickness Modal Confirmation -->
<partial name="_AddSicknessTimeCardModal" />

As you can see I tried using ViewBag to pass the userId but unfortunately it just stores the one id of the last user after iterating over them all. This is the modal for the add sickness leave:

<!-- Modal -->
<div class="modal fade" id="AddSicknessTimeCardModal" tabindex="-1" aria-hidden="true">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <h1 class="modal-title fs-5" id="exampleModalLabel">Mark Absence</h1>
                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
            </div>
            <div class="modal-body">
                <div class="alert alert-warning">
                    <h3>Are you sure you want to mark this person as being sick today?</h3>
                </div>
                <div class="modal-footer">

                    <form asp-action="AddSicknessTimeCard" method="post" asp-route-id="@ViewBag.UserId">
                        <button type="submit" class="btn btn-primary" aria-label="add">Yes</button>
                        <button type="button" class="btn btn-danger" data-bs-dismiss="modal">Cancel</button>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>

My controller needs the userid passed to it to complete the action (the u.Id from the foreach). Any suggestions for passing the id through to the modal partial would be appreciated!