XML解析错误:在ASP.NET Core 2.0 API中找不到根元素

问题描述：

我遇到了这个问题，但无法解决.我正在使用ASP.NET Core 2和Ajax.

I've encountered this problem, and I couldn't figure it out. I'm using ASP.NET Core 2 and Ajax.

这是JavaScript调试器所说的:

This is what the JavaScript debugger says:

XML解析错误:找不到根元素位置: http://localhost:52617/api/favorites/第1行，第1列:>

XML Parsing Error: no root element found Location: http://localhost:52617/api/favorites/ Line Number 1, Column 1:

这是我的JavaScript代码:

This is my JavaScript code:

$(".js-toggle-fav").click(function (e) {
    function sendPost() {
        console.log("inside post send");

        var button = $(e.target);

        $.ajax({
            type: 'POST',
            url: "http://localhost:52617/api/Favorites/",
            data: {"EventId": @Model.Event.EventId},
            contentType: "application/json; charset=utf-8"
        });
    }

    $.getJSON("http://localhost:52617/api/favorites/@Model.Event.EventId", function (data) {
        if (data == null) {
            console.log("fav is null");
            sendPost();
            fav.addClass(toggling);
            fav.text("unfav");
        }
        else {
            console.log("fav is NOT null");
            sendPost();
            fav.removeClass(toggling);
            fav.text("fav");
        }
    );
});

还有我的API:

[HttpPost]
public async Task<IActionResult> PostFavorite([FromBody] FavoriteDto favorite)
{
    if (!ModelState.IsValid)
    {
        Console.WriteLine(ModelState.ValidationState.ToString());
        return BadRequest(ModelState);
    }
    var uid = _userManager.GetUserId(HttpContext.User);
    var fav = await _context.Favourites.SingleOrDefaultAsync(x => x.EventId == favorite.EventId && x.UserId == uid);
    if (fav == null)
    {
        _context.Favourites.Add(new Favorite { EventId = favorite.EventId, UserId=uid });
    }
    else
    {
        _context.Favourites.Remove(fav);
    }
    try
    {
        await _context.SaveChangesAsync();
    }
    catch (DbUpdateException)
    {
        if (FavoriteExists(favorite.EventId))
        {
            return new StatusCodeResult(StatusCodes.Status409Conflict);
        }
        else
        {
            throw;
        }
    }

    return Ok(favorite);
}

当我与Postman或任何restclient一起执行此操作时，所有内容都像魅力一样！使用Ajax并非如此.

When I do this with Postman or any restclient, everything works like a charm! With Ajax, that's not the case.

注意:

在同一个 .cshtml 文件中，还有更多的jQuery和JavaScript代码可以执行类似的操作，并且可以正常工作！所有解决方案不幸的是，我已经检查过互联网无法正常工作.
Get方法(用于返回List或单个元素正在工作！)

In the same .cshtml file, there's more jQuery and JavaScript code which does something like this, and it's just working! All the solutions I've checked on the internet didn't work, unfortunately.
The Get methods (for returning List, or single element are working!)

答

问题来自

data: {"EventId": @Model.Event.EventId},

使用JSON.Stringify

Instead of passing it in directly, use JSON.Stringify

var payload = {EventId: @Model.Event.EventId};
$.ajax({
       type: 'POST',
       url: "http://localhost:52617/api/Favorites/",
       data: JSON.stringify(payload),
       contentType: "application/json; charset=utf-8"
      });

我假设您的FavoriteDto类看起来像这样

I'm assuming your FavoriteDto class looks something like this

public class FavoriteDto
{
   public int EventId { get; set; }
}

出现xml错误的原因是控制器动作

The reason why you were getting an xml error is that the controller action

public async Task<IActionResult> PostFavorite([FromBody] FavoriteDto favorite)

无法解析收藏夹"，因此它从未初始化且为空.然后，您返回ok(null)，当它从服务器接收回响应时，这会在客户端ajax上导致解析错误.

could not parse 'favorite' so it was never initialised and was null. You then return ok(null) which caused a parsing error on your client side ajax when it recieved the response back from your server.

XML解析错误:在ASP.NET Core 2.0 API中找不到根元素

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