Concatenation of values from from asp-for textbox in view to controller not working

Please I am trying to concatenate values from asp-for textboxes and it is not working.

Can you help me show me how it will work?

My controller action and view code is shown below.

CONTROLLER ACTION

[HttpPost]
[ValidateAntiForgeryToken]
public async Task WorkerIdentity([Bind("Id,FirstName,LastName,CompnyCode,DeptmentCode,IdentificationKey,WorkerIdNo")] WorkerIdentity workerIdentity)
{
    if (ModelState.IsValid)
    {
        WorkId Id = new WorkId();
        string? FirstNme = Id.FirstName;
        string? CompCode = Id.CompnyCode;
        string? DeptCode = Id.DeptmentCode;
        string? IdentKey = Id.IdentificationKey;
        string WorkerIdentNo = FirstNme + "." + CompCode + "." + DeptCode + "." + IdentKey;
        RegistrationKeyId WorkerIdentificationNo = new RegistrationKeyId();
        ViewBag.WorkerIdentificationNo = WorkerIdentNo;
        _context.Add(workerIdentity);
        await _context.SaveChangesAsync();
        return RedirectToAction(nameof(Index));            
    }
    return View(workerIdentity);
}

VIEW

@model BootCamp_Opulence.Models.WorkerIdentity

@{
    ViewData["Title"] = "Worker Identity";
}

<h4>@ViewData["Title"] </h4>

<div class="row">
    <div class="col-md-4">
        <form asp-action="WorkerIdentity">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="FirstName" class="control-label"></label>
                <input asp-for="FirstName" class="form-control" name="FirstName" />
                <span asp-validation-for="FirstName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="LastName" class="control-label"></label>
                <input asp-for="LastName" class="form-control" />
                <span asp-validation-for="LastName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="CompnyCode" class="control-label"></label>
                <input asp-for="CompnyCode" class="form-control" name="CompnyCode" />
                <span asp-validation-for="CompnyCode" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="DeptmentCode" class="control-label"></label>
                <input asp-for="DeptmentCode" class="form-control" name="DeptmentCode" />
                <span asp-validation-for="DeptmentCode" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="IdentificationKey" class="control-label"></label>
                <input asp-for="IdentificationKey" class="form-control" value="@ViewBag.WorkerIdKeyNo" name="IdentificationKey" />
                <span asp-validation-for="IdentificationKey" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="WorkerIdNo" class="control-label"></label>
                <input asp-for="WorkerIdNo" class="form-control" value="@ViewBag.WorkerIdentificationNo" />
                <span asp-validation-for="WorkerIdNo" class="text-danger"></span>
            </div><br />
            <div class="form-group">
                <input type="submit" value="Identify" class="btn btn-primary" />
            </div>
        </form>
    </div>
</div>

<div>
    <a asp-action="Index">Back to List</a>
</div>