要扩展 XML 字符串中的变量，您可以使用 自动变量 $ExecutionContext:

To expand variables in an XML string you can use the automatic variable $ExecutionContext:

$str = @'
<config xmlns="http://www.sap.com/lmsl/slp">
  <parameter>
    <id>SidAdmUserName</id>
    <value>$SIDadm</value>
  </parameter>
</config>
'@

$ExecutionContext.InvokeCommand.ExpandString($str)

请注意，这将扩展字符串中的所有 可扩展表达式(例如，$(Get-ChildItem) 之类的内容也会被扩展).

Beware that this will expand all expandable expressions in the string (e.g. something like $(Get-ChildItem) would be expanded as well).

如果您只想在单个元素中扩展一个变量，您可以尝试使用简单的字符串替换:

If you want to expand just a variable in a single element you could try with a simple string replacement:

$str = @'
<config xmlns="http://www.sap.com/lmsl/slp">
  <parameter>
    <id>SidAdmUserName</id>
    <value>$SIDadm</value>
  </parameter>
</config>
'@

$str.Replace('$SIDadm', $SIDadm)

然而，这也可能产生不希望的结果，例如如果有多个变量以相同的部分名称开头.类似的东西

However, that may also yield undesired results, e.g. if there are several variables starting with the same partial name. Something like

<config xmlns="http://www.sap.com/lmsl/slp">
  <parameter>
    <id>SidAdmUserName</id>
    <value>$SIDadm</value>
  </parameter>
  <parameter>
    <id>SidAdmPassword</id>
    <value>$SIDadmPassword</value>
  </parameter>
</config>

会变成

<config xmlns="http://www.sap.com/lmsl/slp">
  <parameter>
    <id>SidAdmUserName</id>
    <value>j3ladm</value>
  </parameter>
  <parameter>
    <id>SidAdmPassword</id>
    <value>j3ladmPassword</value>
  </parameter>
</config>

在这种情况下，***解析 XML，选择特定节点，然后仅替换该节点的内容:

In situations like that it's better to parse the XML, select the particular node, and replace the content of just that node:

[xml]$xml = @'
<config xmlns="http://www.sap.com/lmsl/slp">
  <parameter>
    <id>SidAdmUserName</id>
    <value>$SIDadm</value>
  </parameter>
  <parameter>
    <id>SidAdmPassword</id>
    <value>$SIDadmPassword</value>
  </parameter>
</config>
'@

$nsm = New-Object Xml.XmlNamespaceManager($xml.NameTable)
$nsm.AddNamespace('ns', $xml.DocumentElement.NamespaceURI)

$xpath = '/ns:config/ns:parameter[ns:id/text()="SidAdmUserName"]/ns:value'

$xml.SelectSingleNode($xpath, $nsm).'#text' = $SIDadm
$xml.Save([Console]::Out)

请注意，您必须在此处使用命名空间管理器，因为您的 XML 使用命名空间.

Note that you MUST use a namespace manager here, because your XML uses namespaces.