淘汰赛js，mvc下拉默认值未选择 [英] Knockout js , mvc drop down default value is not selecting

问题描述

这似乎很简单，但我无法做到.

it seems so simple but I am unable to do it.

我已经用来自c#的Json数据限制了一个下拉列表.

I have bounded a Dropdown list with Json data from c#.

查看页面

<div class="col-md-6">
    <select data-bind="options: VehicleTypes, optionsText: 'Name', optionsValue:'ID', optionsCaption: 'All', value: VehicleTypeId" class="form-control"></select>
</div>

杰森(Json)呼叫

淘汰赛模型

var baseModel = {
    VehicleTypeId: null,
    VehicleTypes: [],
}

 var viewModel =  ko.mapping.fromJS(baseModel);

 $.get(urlPath + "/GetVehicleTypes", function (data) {     
      viewModel.VehicleTypes(data);
 });

它确实填满了下拉列表，当我在下拉列表中选择一个值时，会更新VehicleTypeId.

It does fill up the drop down and when I select a value in drop down value gets updated for VehicleTypeId.

我的问题是我想为下拉列表设置默认值，我已经用谷歌搜索过，但对我来说没有什么用

My problem is I want to set a default value for my drop down list, I have googled it but nothing is workign for me

我在Json中获得的数据如下.

Data I am getting back in Json is as follow.

[{
    "ID": 32,
    "Name": "Vehicle 1"
}, {
    "ID": 30,
    "Name": "Vehicle 2"
}, {
    "ID": 31,
    "Name": "Vehicle 3"
}]

推荐答案

您将不得不为VehicleTypeId分配一个值，以便设置默认值.

You will have to assign a value to the VehicleTypeId so that the Default value is set.

此处是一个有效的示例.

Here is a working example.

function VehicleTypesViewModel(){
    var self = this;
  self.VehicleTypeId = null;
  self.VehicleTypes = [];   
}    
var viewModel =  new VehicleTypesViewModel();

$.get(urlPath + "/GetVehicleTypes", function (data) {     
  viewModel.VehicleTypeId = 32;
  viewModel.VehicleTypes = data;
  ko.applyBindings(viewModel);
});

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