Html ActionLink运行时错误：'值不能为null或为空。但值不为null或为空

Question

我试图在我的视图中使用@Html.ActionLink作为可点击链接，但是我得到了运行时异常：

System.ArgumentException：'值不能为null或为空。参数名称：linkText

Html.ActionLink的第一个参数是linkText，正如你从下面的代码中看到的那样，它确实不是空的或空的。

                    @foreach (var o in Model.Results)
                    {
                        <tr>
                            <td>@Html.ActionLink(o.Person.FirstName, "Detail", "Player", new { selectedPlayerID = o.Person.IDPerson, referringController = "ValidationHistory" }, null)</td>
                            <td>@o.Person.FirstName</td>
                            <td>@o.Person.LastName</td>
                            <td>@o.Person.SocialSecurityNumber</td>

下面是页面的屏幕截图，在顶部我嵌入了@（string.IsNullOrWhiteSpace（o.Person.FirstName）？“null / ws”：o.Person.FirstName）如你所见，它确实不是null或空的。

根据请求，下面是与此问题相关的cshtml文件的整个部分。

<div class="col-md-10 text-center">
    @if (Model.Results.Count == 0)
    {
        <h3>No Data to Display</h3>
        <h3>Please Try Different Search Parameters</h3>
    }
    else
    {
        <div id="tablecontaner" class="col-md-10 text-left">
            <table id="PVSearchReport" class="table table-striped table-bordered" style="width:100%;padding:10px">
                <thead>
                    <tr>

                        <th>First Name</th>
                        <th>Last Name</th>
                        <th>SSN</th>
                        <th>IRS / TIN</th>
                        <th>DMF Details</th>
                        <th>List Matches</th>
                        <th>Executed At</th>
                        <th>Executed By</th>
                        <th>Club ID</th>
                        <th>Lists</th>
                    </tr>
                </thead>
                <tbody>
                    @foreach (var o in Model.Results)
                    {
                        <tr>
                            <td>@Html.ActionLink(o.Person.FirstName, "Detail", "Player", new { selectedPlayerID = o.Person.IDPerson, referringController = "ValidationHistory" }, null)</td>
                            <td>@o.Person.FirstName</td>
                            <td>@o.Person.LastName</td>
                            <td>@o.Person.SocialSecurityNumber</td>

                            <td>@o.Validation_Results.IRSOk</td><!--IRS/TIN-->
                            <td>@o.Validation_Results.DMFOk</td><!--DMF Details-->
                            <td>@o.Validation_Results.ListOk</td><!--List Matches-->
                            <td>@o.Validation_Results.ExecutedAt<!--Executed At-->
                            <td>@o.Validation_Results.ExecutedBy</td><!--Executed By-->
                            <td>@o.Person.ClubID</td>
                            <td>@o.ListMatches</td>
                        </tr>
                    }
                </tbody>        
            </table>
        </div>
    }
</div>

Answer 1

我试图重现它。在使用o?.Person?.FirstName和o?.Person?.IDPerson之前需要检查null如果C＃5你可以使用o.Person.FirstName != null ? o.Person.FirstName : "Default Value"这个代码工作了

  <td>@Html.ActionLink(o?.Person?.FirstName, "Detail", "Player", 
new { selectedPlayerID = o?.Person?.IDPerson, referringController = "ValidationHistory" }, null)</td>

Answer 2

1. 首先检查Model是否为null，然后检查o.Person.FirstName是否为null。

           ## Check Model Like: ##
   
            - @if(Model != null && Model.Count() != 0)
               {
                 foreach (var o in Model.Results)
                 {
                   ---------
                 }
               }
           ## Check Record Like: ##
           if(o.Person!=null)
           {
            -----------
           }

Answer 3

我原来的帖子里错了。有一些空字符串被返回。

要解决：

                        @if (o.Person.FirstName == null || o.Person.FirstName == "" || o.Person.FirstName == "NOT")
                        {
                            <td>Not Found</td>
                        }
                        else
                        {
                            <td>@Html.ActionLink(o.Person.FirstName, "Detail", "Player", new { selectedPlayerID = o.Person.IDPerson, referringController = "ValidationHistory" }, null)</td>
                        }

Answer 4

看，你需要先检查循环o.Person这个'Person'对象是否为null而其他是在Person对象中FirstName是否为null，你可以像这样处理它：

 if(o.Person!=null)
    {
        @Html.ActionLink(o.Person.FirstName ?? "Not Found", "Detail", "Player", new { selectedPlayerID = o.Person.IDPerson, referringController = "ValidationHistory" }, null)
    }