[英]Validating null value from DataTable row
我有一个简单的字符串变量,例如:
var currentMedianEmployeeProgressToBackcheck = "";
我像这样填充它:
var EmployeeMedian = (from DataRow dr in dtEmployeeMedian.Rows
select new
{
MedianEmployeeProgressToBackcheck = dr["MedianEmployeeProgressToBackcheck"]
}).FirstOrDefault();
currentMedianEmployeeProgressToBackcheck = EmployeeMedian.MedianEmployeeProgressToBackcheck.ToString();
但是当它为null时,它会抛出null异常:
System.NullReferenceException:'对象引用未设置为对象的实例。
EmployeeMedian为空。
如何在执行该空变量之前对其进行验证? 问候
我尝试简单的,如果喜欢:
if (EmployeeMedian.MedianEmployeeProgressToBackcheck != null){}
但它不起作用
您可以使用Null传播运算符(如果它是C#6或更高版本)(如下所示),确保仅在实例不为null时执行该操作:
currentMedianEmployeeProgressToBackcheck = EmployeeMedian?.MedianEmployeeProgressToBackcheck?.ToString();
否则,您将需要在访问之前放置一个if条件,以确保您未在空引用上调用它,例如:
if(EmployeeMedian !=null && EmployeeMedian.MedianEmployeeProgressToBackcheck != null)
{
currentMedianEmployeeProgressToBackcheck = EmployeeMedian.MedianEmployeeProgressToBackcheck.ToString();
}
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