ASP.NET MVC 4 - 无法对空引用执行运行时绑定

Question

I am trying to output a player's stats in a table. Not all players will have stats depending on the day. I have tried other ways and all are still complaining. Here is the code I have now:

      <tbody>
            @foreach(var player in @ViewBag.Roster){
                int index = 0;
                <tr>
                    <td>@player.Name, @player.TeamName @player.Position</td>
                    if(@ViewBag.Stats[index] == null){
                        <td>--</td>
                        <td>--</td>
                        <td>--</td>
                        <td>--</td>
                    }
                    else{
                        <td>@ViewBag.Stats[index].Points</td>
                        <td>@ViewBag.Stats[index].Rebounds</td>
                        <td>@ViewBag.Stats[index].Assists</td>
                        <td>@ViewBag.Stats[index].Turnovers</td>                        
                    }
                </tr>
                index++;
            }

        </tbody>

Exception Details: Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: Cannot perform runtime binding on a null reference

Source Error:

Line 32: }

Line 33: else{

Line 34: @ViewBag.Stats[index].Points

Line 35: @ViewBag.Stats[index].Rebounds

Line 36: @ViewBag.Stats[index].Assists

Answer 1

OK I am posting the full answer here -

1. Try @ before if(@ViewBag.Stats[index] == null){ and remove @ from @ViewBag inside the if so that it look like this - @if(ViewBag.Stats[index] == null){

2. You are setting index = 0 , inside foreach , so it is initialised in every loop. Initialise it outside foreach like this

   var index = 0; foreach ...

if you are facing problem for the scope try this -

@{
    var index = 0;
    foreach (....) {
        .......
        index++
    }
}

Answer 2

if you want to keep track of the index, why dont you rewrite your loop as:

    var obj = new string[] { "", "", "" };

    for(var index = 0; index < obj.Length; index++)
    {
        var item = obj[index];

        /* DO STUFF WITH ITEM */
    }

    foreach(var item in obj.Select((value, index) => new { index, value }))
    {
        /* DO STUFF WITH item.Value */
    }

Answer 3

I tried both cases suggested above, but with no luck. Then finally I had to initialize my ViewBag collection in the Controller's Index method itself. So when I did something like this,

var stringArray = new string[10] { "", "", "", "", "", "", "", "", "", "" };
ViewBag.doc = stringArray;

it worked. (I had 10 elements. If they were more, had to do something else for initialization.) My code on the view part is as follows now:

  @for (var itm =0; itm< 10; itm++)
                        {
                    <div class="form-group">
                        <label asp-for="Documents[itm].doc"></label>
                        <input type="file" asp-for="Documents[itm].doc" />
                        @if (ViewBag.doc[itm] != "")
                        {<a asp-area="" asp-page="/wwwroot/CaseDocuments/@ViewBag.doc[itm]">@ViewBag.doc[itm]</a>
                            <label asp-for="Documents[itm].remove"></label>
                            @Html.CheckBoxFor(a => a.Documents[itm].remove)
                        }
                    </div>
                            <div class="form-group">
                                <label asp-for="Documents[itm].desc"></label>
                                <textarea asp-for="Documents[itm].desc" class="form-control" rows="3"></textarea>
                            </div>
                        }