在jQuery对WebMethod的AJAX调用中获得空响应，但WebMethod方法返回WebMethod

Question

对于一个jQuery AJAX调用，我将得到空/未定义的响应。我试图在asp.net webforms中将数据绑定到Jquery数据表。当我试图解析数据时，它会在位置1错误的JSON中给出一个意外的标记o。我怀疑问题可能与JSON数据有关，但我已经在JSONlint.com验证了json输出。它一定是我的一些愚蠢的错误，但我无法弄清楚，我浪费了几个小时来解决它。

jQuery Ajax调用

<script type="text/javascript">
    $(function () {
        $('#ShowData').click(function () {
            $.ajax({
                type: "POST",
                contentType: "application/json; charset=utf-8",
                url: 'Default.aspx/fetchDetails',
                dataType: 'json',                    
                data: "{'JobID':'" + $('#txtJobID').val() + "'}",
                success: function (response) {
                    //var d = JSON.parse(data);
                    var data = response.d;
                    alert(typeof (data)); //gives out object
                    alert(response.d); //gives out null
                    $('#tblBasicInfo').dataTable({
                        paging: false,
                        data: data,
                        columns: [
                            { 'data': 'JobId' },
                            { 'data': 'UserId' },
                            { 'data': 'UserName' },
                            { 'data': 'Cas' },
                            { 'data': 'Question' },                                
                            { 'data': 'Language' },
                            { 'data': 'Appl' },
                        ]
                    });
                },
                error: function (xhr, ajaxoptions, thrownError) {
                    alert(xhr.responseText);
                    console.log(xhr.responseText);
                    console.log(xhr.responseJSON);
                }
            });
        });
    });
</script>

WebMethod

 [System.Web.Services.WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public static void fetchDetails(string JobID)
    {
        var conn = System.Configuration.ConfigurationManager.ConnectionStrings["Connection"];
        SqlConnection con = new SqlConnection(conn.ToString());

        String query = "Select TOP 1 * FROM TAble where Jobid =@JobID";
        DataTable dtBasicInfo = new DataTable();
        SqlCommand a = new SqlCommand(query, con);
        a.Parameters.AddWithValue("@JobID", Int32.Parse(JobID));
        con.Open();
        SqlDataAdapter da = new SqlDataAdapter(a);
        da.Fill(dtBasicInfo);
        SqlDataReader value = a.ExecuteReader();
        con.Close();
        JavaScriptSerializer js = new JavaScriptSerializer();

        JavaScriptSerializer jsSerializer = new JavaScriptSerializer();
        List<Dictionary<string, object>> parentRow = new List<Dictionary<string, object>>();
        Dictionary<string, object> childRow;
        foreach (DataRow row in dtBasicInfo.Rows)
        {
            childRow = new Dictionary<string, object>();
            foreach (DataColumn col in dtBasicInfo.Columns)
            {
                childRow.Add(col.ColumnName, row[col]);
            }
            parentRow.Add(childRow);
        }
        var jsk = jsSerializer.Serialize(parentRow);
    }

JSON

[{"JobId":123456789,"UserId":"asdf3a     ","UserName":"Pekki, Barb                      ","Cas":263,"Question":"Q12345","Language":"ENG","Appl":300}]

Answer 1

只要确保在您的代码中实现了以下要点，那么所有这些都会像它应该的那样工作。调用datatable API时使用大写字母D，如$('#tblBasicInfo').DataTable({中所示

1. 您的问题是从您的void中返回一个WebMethod。您需要从C#方法fetchDetails返回一个web对象。
2. 您不需要在WebMethod中创建JSON或进行任何序列化，因为ASP.Net框架将为您工作；只要从您的C#代码中返回一个有效的对象，所有这些都会正常工作。
3. 另外，删除前面提到的数据类型标志，因为这是不需要的fetchDetails方法。由于不需要，我已经从fetchDetails方法中删除了所有序列化代码。只需从web方法中返回类的C#对象即可。

因此，在您的示例中，在方法fetchDetails中定义这个类的一个实例。

作业类

public class Job {

  public int JobId {get;set;}
  public string UserId {get;set;}
  public string UserName {get;set;}
  public int Cas {get;set;}
  public string Question {get;set;}
  public string Language {get;set;}
  public int  Appl {get;set;}

}

fetchDetails方法返回作业类型

[System.Web.Services.WebMethod]
 public static Job fetchDetails(string JobID)
{
    var conn = System.Configuration.ConfigurationManager.ConnectionStrings["Connection"];
    SqlConnection con = new SqlConnection(conn.ToString());

    String query = "Select TOP 1 * FROM TAble where Jobid =@JobID";
    DataTable dtBasicInfo = new DataTable();
    SqlCommand a = new SqlCommand(query, con);
    a.Parameters.AddWithValue("@JobID", Int32.Parse(JobID));
    con.Open();
    SqlDataAdapter da = new SqlDataAdapter(a);
    da.Fill(dtBasicInfo);
    SqlDataReader value = a.ExecuteReader();
    con.Close();

    //WRITE CODE to populate a Job object
     Job job = new Job();
    //set properties of job object before returning it as in code below
   If (dtBasicInfo. Rows. Count > 0)
   { 
    job.JobId =  Int32.Parse(JobID);
    job.UserId = dtBasicInfo.Rows[0]["UserId"].toString();
    job.UserName = dtBasicInfo.Rows[0]["UserName"].toString();
   } 

   return job;
}