How to load 2000+ Records using Ajax Webmethod

Hi experts,

I have a problem in loading a thousand records using ajax it gives me an error "internal Error 500". it can only handled less than 500 records

How can i overcome this problem. Please see my code below thanks in advance.

Webmethod in code Behind

<WebMethod()> _
    Public Shared Function BindDataCountryState(ByVal LocationCode As String) As List(Of ListItem)
        Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("MyConnectionString").ConnectionString)
        Dim CountryState As New List(Of ListItem)()
        Try
  Using con
                Using cmd As New SqlCommand("usp_GetCountryState")
                    cmd.CommandType = CommandType.StoredProcedure
                    cmd.Parameters.AddWithValue("@LocationCode", LocationCode)

                    cmd.Connection = con
                    con.Open()
                    Using sdr As SqlDataReader = cmd.ExecuteReader()
                        While sdr.Read()
                            CountryState.Add(New ListItem() With { _
                              .Value = sdr("Code").ToString(), _
                              .Text = sdr("Description").ToString() _
                            })
                        End While
                    End Using
                    Return CountryState

                End Using
            End Using


        Catch ex As Exception
            HttpContext.Current.Session("error_message") = ex.Message &"
             Return CountryState
        Finally
            If con IsNot Nothing Then
                con.Close()
                con.Dispose()
            End If

        End Try
    End Function

Asp.net Code

var f = document.getElementById("<%=DropDownListPetitionerCountry.ClientID%>");
f.onchange();
var LocationCode = $(f).val();

var parameter = { LocationCode: LocationCode };$.ajax({
                            type: "POST",
                            contentType: "application/json; charset=utf-8",
                            url: "Default.aspx/BindDataCountryState",
                            data: JSON.stringify(parameter),
                            dataType: "json",
                            ////data: '{}',
                            success: function (f) {

                                var ddlCustomers = $("[id*=DropDownListStateProvince]");$.each(f.d, function () {

                                    ddlCustomers.append($("<option></option>").val(this['Value']).html(this['Text']));
                                });
                            },
                            error: function (result) {
                                alert("Error " + result.status);
                                console.log(result.status)
                            }
                        });