我不知道数据是否真的被发送到后面进行处理

Question

所以我正在编写一个小型基本剃须刀页面项目，我有点卡在这部分，我不知道 CategoryId 数据是否真的发送到后端进行处理。我真的不太了解 javascript 我问我的朋友一个 javascript 代码来发送一些数据到后端。这是代码

注：页面为UserMainPage.cshtml和UserMainPage.cshtml.cs

对不起，如果它有点乱，这段代码是供用户使用他们的类别来整理事件。

在 UserMainPage.cshtml 中

<div style="position: relative; margin-left: auto;">
    <select style="height: 40px; border: 1px solid #ddd; border-radius: 4px; padding-left: 10px; font-size: 16px;" id="categorySelect">
        <option value="" hidden>Category</option>
     @if (Model.TblCategory != null && Model.TblCategory.Any())
    {
    foreach (var category in Model.TblCategory)
    {
        <option value="@category.CategoryId">@category.CategoryName</option>
    }
}
else
{
    <option value="0">No categories found</option>
}


    </select>
</div>

这是剧本

<script>
    var categorySelect = document.getElementById('categorySelect');
    categorySelect.addEventListener('change', function () {
        var categoryId = parseInt(categorySelect.value); // convert to integer
        window.location.href = "./UserMainPage?categoryId=" + categoryId;
    });
</script>

在 UserMainPage.cshtml.cs 中

   public async Task<IActionResult> OnPostAsync(int? categoryId, string searchString)
{
    if (categoryId == null && string.IsNullOrEmpty(searchString))
    {
        // If no category is selected and search string is null or empty, return all events
        TblEvent = await _context.TblEvents
            .Include(t => t.Admin)
            .Include(t => t.Category)
            .Include(t => t.Location)
            .ToListAsync();
    }
    else if (categoryId != null)
    {
        // Filter events by category
        TblEvent = await _context.TblEvents
            .Include(t => t.Admin)
            .Include(t => t.Category)
            .Include(t => t.Location)
            .Where(t => t.CategoryId == categoryId)
            .ToListAsync();
    }
    else if (!string.IsNullOrEmpty(searchString))
    {
        // Filter events by search string
        TblEvent = await _context.TblEvents
            .Include(t => t.Admin)
            .Include(t => t.Category)
            .Include(t => t.Location)
            .Where(t => t.EventName.Contains(searchString))
            .ToListAsync();
    }

    return Page();
}