XML解析错误:在ASP.NET Core 2.0 API中找不到根元素 [英] XML Parsing Error: no root element found in ASP.NET Core 2.0 API

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!)

推荐答案

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.

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