检查字符串是不是NULL还是EMPTY

In below code, I need to check if version string is not empty then append its value to the request variable.

在下面的代码中，我需要检查版本字符串是否为空，然后将其值附加到请求变量。

if ([string]::IsNullOrEmpty($version))
{
    $request += "/" + $version
}

How to check not in if condition?

如果有条件，如何检查？

4 个解决方案

if (-not ([string]::IsNullOrEmpty($version)))
{
    $request += "/" + $version
}

You can also use ! as an alternative to -not.

你也可以用！作为-not的替代。

You don't necessarily have to use the [string]:: prefix. This works in the same way:

您不一定要使用[string] ::前缀。这以同样的方式工作：

if ($version)
{
    $request += "/" + $version
}

A variable that is null or empty string evaluates to false.

null或空字符串的变量求值为false。

As in many other programming and scripting languages you can do so by adding ! in front of the condition

与许多其他编程和脚本语言一样，您可以添加！在条件面前

if (![string]::IsNullOrEmpty($version))
{
    $request += "/" + $version
}

If the variable is a parameter then you could use advanced function parameter binding like below to validate not null or empty:

如果变量是参数，那么您可以使用如下的高级函数参数绑定来验证非null或空：

[CmdletBinding()]
Param (
    [parameter(mandatory=$true)]
    [ValidateNotNullOrEmpty()]
    [string]$Version
)

if (-not ([string]::IsNullOrEmpty($version)))
{
    $request += "/" + $version
}