webmethod显示500（内部服务器错误）

Question

I am trying to call a webmethod from alertBook.aspx.vb. But I received an error 500 (internal Server Error) whenever I click on button.

Is this a right way to call the webmethod from javascript? I am new to javascript.

Thanks in advance.

My javascript as follow:

function webMethod() {
                setInterval(function () {
                    $.ajax({
                        type: "post",
                        url: "alertBook.aspx/newUid",
                        contentType: "application/json; charset=utf-8",
                        dataType: "json",
                        success: function (result) {
                            OnSuccess(result);
                        },
                        error: function (xhr, status, error) {
                            OnFailure(error);
                        }
                    });
                }, 3000);
            }
            function OnSucceeded(response) {
                alert(response);
                //pushNoti(response, "info", "y");
            }

            function OnFailure(error) {
                alert(error);
            }

alertBook.aspx is

<a class="btn btn-info" onclick="webMethod()">WebMethod</a>

My webmethod as follow:

<WebMethod()> _
    Public Shared Function newUid(ByVal msg As String) As String

        Dim objForm As New alertBook

        Dim objUtl As New uClass.fUtilities

        Dim sqlQuery As String
        Dim UID1, UID2 As String
        Dim notiStr As String
        Dim objDb As New uClass.dbFunctions("myCon")

        Dim dtRecords As DataTable

        sqlQuery = "select top 1 UID from alertsBook order by UID desc"

        If objDb.getDataTable(dtRecords, sqlQuery) = False Then
            Return objForm.displayMessage("Error", objDb.errDesc)
        End If

        For rCount = 0 To dtRecords.Rows.Count - 1
            UID1 = dtRecords.Rows(rCount)("UID")
        Next

        If UID1 <> UID2 Then
            notiStr = "<script> " & displayNoti("", "info", "New Message", True) & "</script>"
            UID2 = UID1
            'scriptDiv.InnerHtml = notiStr
        Else
            notiStr = ""
        End If

        Return notiStr

    End Function

Answer 1

You should look for more detail on the error. You can use

  error: function (xhr, status, error){
    alert(xhr.status);
    alert(xhr.responseText);
  }

xhr.responseText contains detail information about the ajax-error.
do get more detail or the error and change you code accordingly.