可为空的日期时间异常

Question

On respository, I have nullable string " o.Attribute("PreorderLanchDate")" converted to nullable datetime .

Here is the code:

PreorderLanchDate = o.Attribute("PreorderLanchDate") == null ? (DateTime?)null : DateTime.Parse(o.Attribute("PreorderLanchDate").Value), 

On controller, launchdate is nullable, not getting the value, as it is showing the null value exception. here is the code:

LaunchDate = (DateTime)product.PreorderLanchDate

Answer 1

Try this.

  //along with the null reference check, Use `String.IsNullOrEmpty` to check o.Attribute("PreorderLanchDate").Valuen
 PreorderLanchDate = o.Attribute("PreorderLanchDate") == null || String.IsNullOrEmpty(o.Attribute("PreorderLanchDate").Value) ? (DateTime?)null : DateTime.Parse(o.Attribute("PreorderLanchDate").Value), 



  //Cast to a nullable DateTime
LaunchDate = (DateTime?)product.PreorderLanchDate

Answer 2

product.PreorderLaunchDate是可为null的DateTime ，如果其值为null ，则将强制将其强制转换为正常的DateTime 。

Answer 3

You can use the as operator to perform certain types of conversions between compatible reference types or nullable types.

var nullableDateTime = product.PreorderLanchDate as DateTime;

if ( nullableDateTime != null )
    LaunchDate = nullableDateTime;