来自Web服务的DropDownList绑定在asp.net中编辑时不传递数据源答案

【问题标题】：DropDownList bind from web service Not passing data source when Edit in asp.net来自Web服务的DropDownList绑定在asp.net中编辑时不传递数据源
【发布时间】：2018-12-13 13:04:10
【问题描述】：

当我添加新数据下拉列表工作正常时，我正在使用 Web 服务绑定 DropDownList 中的数据，但是当我编辑模式时删除数据源未填充。所以问题是当我使用web服务绑定web服务时如何填充数据源。

HTML：

<asp:DropDownList ID="cmbFlightNo" class="form-control"  runat="server" DataValueField="mFlightNo" DataTextField="mFlightNo" AppendDataBoundItems="true">

                        </asp:DropDownList>

网络服务

[WebMethod]
public Airline_Flights[] Loadetails(string StuID)
{
    string Conec = ConfigurationManager.ConnectionStrings["BriskCargo"].ConnectionString;
    SqlConnection con = new SqlConnection(Conec);
    con.Open();
    SqlDataAdapter da = new SqlDataAdapter("Select FlightNo from AirLine_Flights where ALCode='" + StuID + "' and IsActive=1", con);
    DataTable st = new DataTable();
    da.Fill(st);
    List<Airline_Flights> details = new List<Airline_Flights>();
    foreach (DataRow dtrow in st.Rows)
    {
        Airline_Flights obj = new Airline_Flights();
        obj.mFlightNo = dtrow["FlightNo"].ToString();
        details.Add(obj);
    }
    JavaScriptSerializer ser = new JavaScriptSerializer();
    return details.ToArray();
}

触发时更改时填充的JQuery代码。

 function Load_Regno() {

       var StuID = document.getElementById('ContentPlaceHolder1_cmbAirlines').value;
      $.ajax(
        {
        type: "POST",
           contentType: "application/json;charset=utf-8",
           url: "AirlinesDropDown.asmx/Loadetails",
           data: JSON.stringify({StuID: StuID }),
           dataType: "json",
           success: function (data) {
             var theDropDown = document.getElementById("ContentPlaceHolder1_cmbFlightNo");
             theDropDown.length = 0;
             $.each(data.d, function (key, value) {
                 $("#ContentPlaceHolder1_cmbFlightNo").append($("<option></option>").val(value.mFlightNo).html(value.mFlightNo));
    });
            },
           error: function (XMLHttpRequest, textStatus, errorThrown) {
              if (XMLHttpRequest.status == 0) {
        alert(' Check Your Network.');
    } else if (XMLHttpRequest.status == 404) {
        alert('Requested URL not found.');
    } else if (XMLHttpRequest.status == 500) {
        alert('Internel Server Error.');
    } else {
        alert('Unknow Error.\n' + XMLHttpRequest.responseText);
    }
              }
        });

            return false;
   }

【问题讨论】：

看来你不使用JavaScriptSerializer ser = new JavaScriptSerializer(); 所以可能删除它。你签入调试器，return details.ToArray(); 是否包含数据？对不起，基本问题，试图在这里找到失败点。当绑定服务器端时，Webforms 往往希望您使用服务器端方法、更新面板等。

标签： c# jquery asp.net web-services

【解决方案1】：

[WebMethod]
public Airline_Flights[] Loadetails(string StuID)
{
    var flightsList = GetFlightListByStuID(string StuID);
    return selectedFlights.Select(x => x.FlightNo).ToArray();
}

// could be in another data access class etc.
private List<Airline_Flights> GetFlightListByStuID(string StuID)
{
    List<Airline_Flights> selectedFlights = new List<Airline_Flights>();
    string connectionString = ConfigurationManager.ConnectionStrings["BriskCargo"].ConnectionString;
    // SQL with parameter
    string commandString = @"
       SELECT FlightNo 
       FROM AirLine_Flights 
       WHERE ALCode = @StuID AND IsActive=1
      ";

    // use IDisposable here so it closes and garbage collects automatically
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        using (SqlCommand command = new SqlCommand(commandString))
        {
            // check the length and type here...
            command.Parameters.Add("@StuID",SqlDbType.NVChar, 25).Value = StuID; 
            command.CommandType = CommandType.Text;
            using (var reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                   flightsList.Add(new Airline_Flights{ FlightNo= reader["FlightNo"].ToString()});
                }
            }
        }  
    }
    return selectedFlights;
}

JavaScript

function Load_Regno() {
  var StuID = document.getElementById('ContentPlaceHolder1_cmbAirlines').value;
  $.ajax({
      type: "POST",
      contentType: "application/json",
      url: "AirlinesDropDown.asmx/Loadetails",
      data: {StuID: StuID},
      dataType: "json"
    })
    .done(function(data) {
      // verify data
      alert(JSON.stringify(data));
      // or
      console.log(data);
      var theDropDown = $("ContentPlaceHolder1_cmbFlightNo");
      theDropDown.html(""); // clear old options
      var options = [];
      $.each(data.d, function(key, value) {
         var opt = ("<option></option>").val(value.FlightNo).html(value.FlightNo))
         options.push(opt); 
      });
      $.each(options,function(v){theDropDown.append(v);});
    })
    .fail(function(XMLHttpRequest, textStatus, errorThrown) {
        if (XMLHttpRequest.status == 0) {
          alert('Check Your Network.');
        } else if (XMLHttpRequest.status == 404) {
          alert('Requested URL not found.');
        } else if (XMLHttpRequest.status == 500) {
          alert('Internal Server Error.');
        } else {
          alert('Unknown Error.\n' + XMLHttpRequest.responseText);
        }
      }
    });
    return false;
}

【讨论】：