Question

我有一种将WebGrid导出到.csv文件的方法，但并非所有 Surveys 都包含 CompanyName ，因此我收到错误＆＃39;未设置对象引用到一个对象的实例。＆＃39;

我该怎么做才能纠正这个问题？

    public void DownloadCSV()
    {

        StringWriter sw = new StringWriter();

        sw.WriteLine("\"Project Number\",\"Location\"");

        Response.ClearContent();
        Response.AddHeader("content-disposition", "attachment; filename=Survey" + DateTime.Today.ToShortDateString() + ".csv");
        Response.ContentType = "text/csv";

        var surveys = from s in SurveyDB.Surveys select s;

        foreach (var line in surveys)
        {
                sw.WriteLine(string.Format("\"{0}\",\"{1}\",\"{2}\"",
                                           line.projNo,
                                           line.locationName,
                                           line.Company.CompanyName
                                           ));
        }

        Response.Write(sw.ToString());

        Response.End();

    }

Answer 1

试试这个：

 sw.WriteLine(string.Format("\"{0}\",\"{1}\",\"{2}\"",
    line.projNo,
    line.locationName,
    (line.Company == null || line.Company.CompanyName == null) ? "" : line.Company.CompanyName
 ));

如果您使用的是Entity Framework，我建议您从以下位置更新此行：

var surveys = from s in SurveyDB.Surveys select s;

要：

var surveys = from s in SurveyDB.Surveys.Include("Companies") select s;

对象引用未设置为对象的实例 - MVC 4 - WebGrid Export

1 个答案: