<div class="result2">
<table class="table table-bordered">
    <thead>
        <tr>
            <th>@Html.DisplayNameFor(m => m.ThermLossesDataInput.LyingTypeOne)</th>
       </tr>
    </thead>
    <tbody>
        @foreach (ThermLossesDataInput item in Model.ListThermLossesDataInputs)
        {
            <tr>
                <td>@item.LyingTypeOne</td>
                <td>
                    <form method="post">
                       //один из способов (пробовал через ViewBag)
                        @{ ViewBag.ThermLossesDataInputId = item.ThermLossesDataInputId; }
                        <input type="hidden" asp-for="@item.ThermLossesDataInputId" />
                        <input type="button" class="btn btn-info" id="delete" value="del" />
                    </form>
                </td>
            </tr>
        }
    </tbody>
</table>

$(document).ready(function () {
        $('#delete').click(function () {
            $.ajax({
                type: 'POST',
                dataType: 'html',
                data: $('form').serialize(),
                // вариант с неправильными данными??? какой должен быть URL.Action?
                url: '@Url.Action("DeleteDataInputWaterPipelines", "ThermLosses", new { ViewBag.ThermLossesDataInputId })',

                success: function (data) {
                    $('#results').html(data);
                }
            });
         });

[HttpPost]                                              // 0!!
    public IActionResult DeleteDataInputWaterPipelines(int ThermLossesDataInputId)
    {

        WaterPipelineViewModel model = new WaterPipelineViewModel();
        ThermLossesDataInput thermLossesDataInput = _context.ThermLossesDataInputs.SingleOrDefault(m=>m.ThermLossesDataInputId == ThermLossesDataInputId);
        int thermLossesMainId = thermLossesDataInput.ThermLossesMainId;

        _context.ThermLossesDataInputs.Remove(thermLossesDataInput);
        _context.SaveChanges();

        model.ListThermLossesDataInputs = _context.ThermLossesDataInputs.Where(m => m.ThermLossesMainId == thermLossesMainId).ToList();
        return PartialView("_DataTable", model);
    }

<form method="post">
      <input type="hidden" value="@item.ThermLossesDataInputId" id="thdi"/>
      <input type="button" class="btn btn-info" id="delete" value="del" />
 </form>

$(document).ready(function () {
      $('#delete').click(function () {
                var id = $('#thdi').val();
                $.ajax({
                    type: 'POST',
                    dataType: 'html',
                    data: { 'id' : id },
                    url: '@Url.Action("DeleteDataInputWaterPipelines", "ThermLosses")',
                    success: function (data) {
                        $('#results').html(data);
                    }

                });
            });