string.isnullorempty(字符串)不起作用 [英] string.isnullorempty(string) is not working

问题描述

我有问题.
在数据库日期字段中包含空值或空值.
将日期字段加载到前端时，我想替换系统日期.而不是vb.net中的空字段.
尝试解决此查询时，String.isnullorempty(string)在.Net2003中不起作用.
您能解决我的问题吗?

Hi,
I have a problem.
At Database Datefield containing empty or null value.
While loading the date field to front end I want to replace system date. instead of empty field in vb.net.
And String.isnullorempty(string) is not working in .Net2003 while try to solve this query.
Can u solve my problem

推荐答案

如果从数据库中检索空值，它将是DBNull.Value而不是null.首先进行测试.

If you retrieve a null value from the database, it will be DBNull.Value rather than null. Test for that first.

看看此链接底部给出的所有其他方法(用于IsNullOrEmpty) [ ^ ].

Have a look at all alternate methods (for IsNullOrEmpty) given towards the bottom of this link[^].

=== Version 1 (C#) ===

// Test version 1.
if (s == null || s == "")
{
    Console.WriteLine("1");
}

=== Version 3 (C#) ===

// Test version 3.
if (s == null || s.Length == 0)
{
    Console.WriteLine("3");
}

日期字段为空时为DBNull.不是Null或"
一个快速解决问题的方法是:String.IsNullOrEmpty(myString.toString)
或检查是否为DBNull.

The datefield is DBNull when empty. Not Null or ""
A quick solution for your problem would be: String.IsNullOrEmpty(myString.toString)
Or to check for DBNull.

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