Question

我在我的一个控制器中有以下代码块，此代码返回两个日期字符串，这些日期字符串根据我的View消费文化以某种方式格式化。

string dateStringForSystem = "";
string dateStringForActiveMetrics = "";
string cultureConfigKey = System.Configuration.ConfigurationManager.AppSettings["InstanceCulture"];
DateTime? lastEntryDateForSystem = null;
DateTime? lastEntryDateForActiveMetrics = null;
DataSet dSet = DataHelper.Measurements_GetLastMeasurement(userSession.UserIDNative);                

foreach (DataRow dr in dSet.Tables[0].Rows)
{
    lastEntryDateForSystem = (DateTime?)dr["LastMeasurementWhen"];
    lastEntryDateForActiveMetrics = (DateTime?)dr["LastMeasurementForActiveGoalsWhen"];             
}

// Format viewdata dates based on culture and convert it to string
if (cultureConfigKey == "en" )
{                
    ViewData["DateStringForSystem"] = dateStringForSystem = String.Format("{0:MM/dd/yy}", lastEntryDateForSystem);
    ViewData["DateStringForActiveMetrics"] = dateStringForActiveMetrics = String.Format("{0:MM/dd/yy}", lastEntryDateForActiveMetrics);
}
else
{
    ViewData["DateStringForSystem"] = dateStringForSystem = String.Format("{0:dd/MM/yy}", lastEntryDateForSystem);
    ViewData["DateStringForActiveMetrics"] = dateStringForActiveMetrics = String.Format("{0:dd/MM/yy}", lastEntryDateForActiveMetrics);
 }

在View代码中，我存储并使用视图数据。但是如果字符串返回null我就会收到错误。即使我将dateTime转换为字符串，null也不会作为字符串返回吗？

var dateStringForSystem = ViewData["DateStringForSystem"];
var dateStringForActiveMetrics = ViewData["DateStringForActiveMetrics"];

    @if (dateStringForSystem == "")
    {
        // some html
    }
    else if (dateStringForActiveMetrics != "")
    {
       <span>@dateStringForActiveMetrics</span>
    }

对于C＃来说还是一个新手，所以有关清理此代码的任何建议也非常感谢:)谢谢！

DateTime转换为字符串时获取错误返回null

0 个答案: