Today I got the question<\/p>\n
\nI\u2019ve looked into all of my.format.ps1xml files but I can\u2019t find out where Format-List is getting its default view for, say, System.Diagnostics.Process:<\/em><\/p>\n
PS> ps |select -first 1 |fl<\/strong> <\/font><\/p>\n
Id : 7616
Handles : 543
CPU : 10.6860685
Name : CmdletDesigner<\/font><\/p>\nHow does it know it should display just these four properties?
It seems there isn\u2019t any ListControl view selected by this type within those formatting files…<\/em><\/p>\n<\/blockquote>\nExcellent question! Let\u2019s pick behind the curtain and see how it works. When an object gets to one of our formatting commands, we use its type to look and see if there is a VIEW defined for it. These views are defined in our formatting files in $PSHOME directory. They have filenames like xxx.Format.ps1xml . If we find it, we use it. If we don\u2019t find it, we look to see whether this type has a DefaultDisplayPropertySet defined. If it does, we use it. If it doesn\u2019t we emit all the properties either as a table or a list depending upon how many properties there are.<\/p>\n
<\/p>\n
But wait a minute \u2013 let\u2019s go back and look at this DefaultDisplayPropertySet \u2013 what\u2019s that all about? If you\u2019ve been using PowerShell a while, you\u2019ll realize that PowerShell uses a type mashup system. Mashups are really just an identity space and a mechanism for 3rd parties to add addition information into an identity space. For map mashups, the identity space is latitude\/longitude and a mechanism for someone to provide the lat\/long for all the Starbucks in the world. For PowerShell, we use TYPEs as an identity space and then have various mechanisms for 3rd parties to add extra information. One of those mechanisms is TYPE files (e.g. $pshome\/types.ps1xml ). If you take a look at the file, you\u2019ll see that we have a set of entries which are keyed off of a typename and can add extra information. If you search for System.Diagnostics.Process \u2013 you\u2019ll see a bunch of stuff. One of the things you can add to a type is a MemberSet<\/p>\n
<\/p>\n
One of the things you\u2019ll see is a super double secret MemberSet called PSStandardMembers. This is a hidden memberset that PowerShell uses for it\u2019s own purposes. In that memberset, you (we) can define something called DefaultDisplayPropertertySet which provides a set of properties that should be displayed if there isn\u2019t a view defined. Let me show you that it is really there (you can follow along at home):<\/p>\n
PS> $x = Get-Process |Select -First 1
<\/strong>PS> $x |Format-List<\/strong><\/font><\/p>\nId : 7616
Handles : 543
CPU : 10.7172687
Name : CmdletDesigner <\/font><\/p>\n<\/font><\/p>\n
PS> # Let me prove to you that it is hidden
PS> $x |Get-Member PSStandardMembers<\/strong>
<\/font><\/p>\n
<\/font><\/p>\nPS> # It’s really there, just hidden. You can show hidden things using -Force
PS> $x |Get-Member PSStandardMembers -Force <\/strong><\/font><\/p>\nTypeName: System.Diagnostics.Process <\/font><\/p>\n
Name MemberType Definition
—- ———- ———-
PSStandardMembers MemberSet PSStandardMembers {DefaultDisplayPropertySet}<\/font><\/p>\n<\/font><\/p>\n
<\/font><\/p>\n
PS> $x.PSStandardMembers<\/strong>
PSStandardMembers {DefaultDisplayPropertySet}
<\/font><\/p>\n
PS> $x.PSStandardMembers.DefaultDisplayPropertySet<\/strong> <\/font><\/p>\nReferencedPropertyNames : {Id, Handles, CPU, Name}
MemberType : PropertySet
Value : DefaultDisplayPropertySet {Id, Handles, CPU, Name}
TypeNameOfValue : System.Management.Automation.PSPropertySet
Name : DefaultDisplayPropertySet
IsInstance : False <\/font><\/p>\n<\/font><\/p>\n
<\/font><\/p>\n
PS> $x.PSStandardMembers.DefaultDisplayPropertySet.ReferencedPropertyNames
<\/strong>Id
Handles
CPU
Name
PS><\/p>\n<\/p>\n<\/p>\n
Now it really isn\u2019t secret we just haven\u2019t talked about it much. It is documented @ MSDN HERE<\/a> .<\/p>\n
PSStandardMembers is used for a number of things in addition to DefaultDisplayProperties. In particular, it is used to control object serialization. You can find out more about that in my blog entry HERE<\/a>.<\/p>\n
<\/p>\n
Enjoy! <\/p>\n
Jeffrey Snover [MSFT]
Distinguished Engineer
Visit the Windows PowerShell Team blog at: http:\/\/blogs.msdn.com\/PowerShell<\/a>
Visit the Windows PowerShell ScriptCenter at: http:\/\/www.microsoft.com\/technet\/scriptcenter\/hubs\/msh.mspx<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Today I got the question I\u2019ve looked into all of my.format.ps1xml files but I can\u2019t find out where Format-List is getting its default view for, say, System.Diagnostics.Process: PS> ps |select -first 1 |fl Id : 7616 Handles : 543 CPU : 10.6860685 Name : CmdletDesigner How does it know it should display just these four […]<\/p>\n","protected":false},"author":600,"featured_media":13641,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-3091","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-powershell"],"acf":[],"blog_post_summary":"
Today I got the question I\u2019ve looked into all of my.format.ps1xml files but I can\u2019t find out where Format-List is getting its default view for, say, System.Diagnostics.Process: PS> ps |select -first 1 |fl Id : 7616 Handles : 543 CPU : 10.6860685 Name : CmdletDesigner How does it know it should display just these four […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/3091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/users\/600"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/comments?post=3091"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/posts\/3091\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media\/13641"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/media?parent=3091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/categories?post=3091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/powershell\/wp-json\/wp\/v2\/tags?post=3091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}