数据成功插入但ajax抛出错误

Question

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，这是我的ajax调用功能

document.getElementById("btnSubmit").onclick = function ()
{
    var txtImageName = $('#txtImageName').val();
    var CategoryId = $('#cmbCategory').val();
    var ImageURL = $('#txtImageURL').val();
    var ImageSource = $('#textEditor').val();
    var value = CKEDITOR.instances['textEditor'].getData()

    alert
    $.ajax({
        url: "UrlwebService.asmx/InsertImage",
        type: 'POST',
        data: { ImageName: txtImageName, ImageUrl3x:ImageURL,ImageSource:value,CategoryId:parseInt(CategoryId) },
        dataType: 'json',
        contentType: "application/x-www-form-urlencoded",
        success: function (Categories) {               
            // states is your JSON array
               alert(Categories);
        },
        error: function (xhr, err) {
            alert("I'm in terror");
            alert("readyState: " + xhr.readyState + "\nstatus: " + xhr.status);
            alert("responseText: " + xhr.responseText);
        }
    });
};

我将内容类型更改为application / json它也会让我犯错误 在这里我称这种方法.....

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json, UseHttpGet = true)]
public void InsertImage(string ImageName, string ImageUrl3x, string     ImageSource, int CategoryId)
{
    var result = ImageRepo.InsertImage(ImageName,ImageUrl3x,ImageSource,CategoryId);
    var js = new System.Web.Script.Serialization.JavaScriptSerializer();            
    Context.Response.Write(js.Serialize(result));
}