Powershell Set-Variable resets Variable instead of updating it

Question

I'm confused on how to use Set-Variable to change a specific value in a variable. I don't understand the resulting behavior. I am trying this in Powershell 5.1.

If I create a new variable with New-Variable

New-Variable -Name TestVariable -Value @{Name1 = 'Value1'; Name2 = 'Value2'}

And then I try to change it with Set-Variable

Set-Variable -Name TestVariable -Value @{Name1 = 'NewValue'}

Why is my output now:

Name                           Value
----                           -----
Name1                          NewValue

and not as expected:

Name                           Value
----                           -----
Name1                          NewValue
Name2                          Value2

Set-Variable appears to reset the whole variable instead of changing it. Or creating a new variable without the -Force setting, which is kind of scary.

The description from the Microsoft docs say:

The Set-Variable cmdlet assigns a value to a specified variable or changes the current value. If the variable does not exist, the cmdlet creates it.

Do I misunderstand the or changes part somehow?

I've also tried to store the parameters in a variable itself instead of writing it out after the -Value however that results in the same behavior as expected.

Now if I do change the value without Set-Variable it works just fine.

$TestNewVariable.Name1 = 'NewValue'

and the output is exactly as expected:

Name                           Value
----                           -----
Name1                          NewValue
Name2                          Value2

The Solution would be instead of changing a value in the variable is to just write all values again. However I'd be very interested to know why the Set-Variable is not just changing the value or what I am doing wrong.

Answer 1

不像名称Set-Variable可能暗示它用于编辑变量值，它仅用于编辑变量属性，例如 -Scope、-Visibility、-Description 等。其中可以是变量的 -Value，但只能将 Value 作为整体而不是值属性，因为Set-Variable在任何时候都不关心值属性，因此无法编辑它们。