替代方式转换int？加倍？

Question

有没有办法转换这个？

public int? intVal ;
public double? dblVal ;

我现在的工作方式

if(dblVal==null)
    intVal =null;
else
    intVal = Convert.ToInt32(dblVal);

还有其他办法吗？提前致谢 .

Answer 1

刚演员:

intVal = (int?) dblVal;

This will already result in a null value if dblVal is null. Note that unlike Convert.ToInt32(double), this does not result in an exception if dblVal is outside the range of int. If that's a concern, you should work out exactly what you want to achieve.

From the C# 5 spec, section 6.2.3:

Explicit nullable conversions permit predefined explicit conversions that operate on non-nullable value types to also be used with nullable forms of those types. For each of the predefined explicit conversions that convert from a non-nullable value type S to a non-nullable value type T (§6.1.1, §6.1.2, §6.1.3, §6.2.1, and §6.2.2), the following nullable conversions exist:

• S的显式转换？到T？.
• 从S到T的显式转换？
• S的显式转换？对T.

基于从S到T的基础转换的可空转换的评估进行如下:

• 如果可空转换来自S？到T？:
  • 如果源值为null(HasValue属性为false),则结果为类型T？的空值.
  • 否则,转换被评估为从S展开？到S,然后是从S到T的底层转换,接着是从T到T？的包装.
• ...