检查DateTime变量是否已分配值 [英] Checking to see if a DateTime variable has had a value assigned

问题描述

解决方案

在C＃中有一个简单的方法来检查一个DateTime实例是否被赋值>在C＃中没有赋值的变量的唯一方法是将其作为局部变量 - 在这种情况下，在编译时，您可以通过尝试从中读取它来确定它不是绝对分配的我想你真的想要 Nullable< DateTime> （或 DateTime？

/ code>与C＃语法糖） - 使它 null 开始，然后分配一个正常的 DateTime 值（将被适当转换）。然后，您可以与 null （或使用 HasValue 属性）进行比较，以查看是否已经有真实值设置。

Is there an easy way within C# to check to see if a DateTime instance has been assigned a value or not?

解决方案

The only way of having a variable which hasn't been assigned a value in C# is for it to be a local variable - in which case at compile-time you can tell that it isn't definitely assigned by trying to read from it :)

I suspect you really want Nullable<DateTime> (or DateTime? with the C# syntactic sugar) - make it null to start with and then assign a normal DateTime value (which will be converted appropriately). Then you can just compare with null (or use the HasValue property) to see whether a "real" value has been set.

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