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Obviously,

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there is a lot more that we can do and will want to do with hashtables.

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So once again,

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let's go back into PowerShell and let me demonstrate

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how you can work with hashtables.

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To create a hashtable, you can either create an empty hashtable like this,

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so $ht = @ symbol and a set of curly braces,

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or you can create a hashtable and assign values as you create it.

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This hashtable has three key value pairs.

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The first one is name with the value of jeff,

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count, which has a value of 3, and then Sample Entry,

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which has a value of This is something.

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Notice that sample entry has double quotes around the name of the

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key and that's because there is a space in that.

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Typically, I would avoid using spaces in my keys,

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it just simplifies everything in PowerShell,

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but if you need to have it, that's how you would do it.

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Because I'm doing this all on one line,

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I use a semicolon to separate the key value pairs.

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The hashtable is its own special type of object.

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You can see there it's a System.Collection.Hashtable,

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and if you want to view the hashtable,

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just obviously look at the variable and there we go.

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So there are my three keys which show up as name and

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then the value that goes with each one.

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If I want to, I can add an element to the hashtable,

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so I'm going to add a key called version with a value of 7.

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Now you can see there is my new entry.

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If I want to, I can also change values in the hashtable.

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So I'm going to take that count property and use the ++ operator which

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will take the value of count and increment it by 1,

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and sure enough, it is now 4, or I can also assign a new value such as 10.

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You can reference elements by their key name.

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So if I want to get the name entry from the hashtable,

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I can do $ht.Name and I get Jeff as the result.

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There are a couple other ways that you can reference items in a hashtable.

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You can use this syntax where you put the key name in square brackets,

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it gives you then the value,

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and I think this approach is easier if you have a

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key that has a space in the name.

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Another option that you can use is the item method and all you

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have to do is specify the name of the key,

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in this case, name and I get the result of Jeff.

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With hashtables,

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you can list all of the keys and you can also list all of the values.

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If you need to remove an element from an array,

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there is a remove method and just specify the key.

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There is nothing really that shows you that it's

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gone until you look at it again.

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It is possible to completely remove all of the entries

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in the array using the clear method.

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And now if I do $ht, I can see that there is nothing in it.

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The variable still exists, but is an empty hashtable.

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You can use hashtables to really store just about anything that you want.

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So let's build another hashtable.

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I'll create my entry name and now I'll do the count again for 3.

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Notice that because I'm not doing this all on the same line,

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I don't have to put in the semicolon.

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As soon as I hit Enter,

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PowerShell knows the next thing that I type is

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going to be another key value pair, so I don't have to use semicolons here.

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You can if you want, but it's not required when you're doing it this way.

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So let's run Get‑Process and get the PowerShell

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process and save that to the key ps.

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Let's skip all of the services, and this time just to keep it interesting,

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I'm going to use Get‑CimInstance to retrieve all

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instances of the win32_service class, save that to the key services.

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You can also create nested hashtables.

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So I'm going to create another hashtable here,

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has keys of foo, vendor, and color,

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and that will then become a nested hashtable in the hashtable $ht.

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There is really no end to how far you can go or need to go.

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Put in my closing curly brace and that defines then the hashtable $ht.

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It took a moment because it had to go and get all of those services.

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So what's in $ht now?

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Alright, so there is the name, there is my nested property,

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the count services, and the PS key.

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Let's look at these items a little more closely.

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So I have a hashtable that has a key of services and

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the value of services is an array, which means I can use array techniques,

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such as getting the first five services in that element,

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and there we go.

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If I want to get the PS key, which is the PowerShell process, there we go.

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Again, this is just another object,

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and I can continue to use the object.notation.

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So if I want to get the CommandLine property of that object,

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sure enough, that's pretty simple to do.

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Let's look at the nested hashtable.

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So there is my necid hashtable.

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Again, I can continue to use the dotted notation.

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If I want to, I can change the color entry in that nested hashtable to red,

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and now that nested hashtable has an updated value.

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There is no limit really to what you can do and how

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you might want to use a hashtable.

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Now, one thing I want to point out, let's go back and look at $ht,

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you can see that it's listed here as Name,

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nested, account, services, and ps as the keys,

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but that is not the order that I created the entries.

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Hashtables are unordered,

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meaning there is no guarantee that it will be displayed in the same

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order that you created or added the key value pairs.

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If you need that, there is a way to do that and we're going to do it like this.

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You're still going to create a hashtable the same way.

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The only difference is we're going to stick a little tag in

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front of it called ordered and that tells PowerShell treat

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this as a special type of hashtable, an ordered hashtable.

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So now if I look at k,

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the keys are listed in the same order that I entered them or

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created them in the hashtable so I've got first,

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second, and third.

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Technically, this is a different type of object than the hashtable.

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Now you can see this is a ordered dictionary object which is different

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technically from a .NET perspective than a hashtable.

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However, we still use them the same way.

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You can still reference items by their property names,

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and if you want, you can change the value.

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So nothing really changes in that regard.

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The only thing that changes is that the order of the key names is different

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if you use ordered versus just a traditional hashtable.

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Of course, you should read the help topic about hashtables to learn even more.

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Next let me show you some practical ways to use hashtables.

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The first step is splatting, and this is how splatting works.

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First,

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let me show you a command like Get‑Service that you would

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normally run and this is using parameters,

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‑name and ‑exclude.

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So I'm going to get all the services that start with the letter B,

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but exclude the bits service.

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Now what I'm going to do is define a hashtable and the keys of the hashtable,

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Name and Exclude, are going to match the name of the parameters for Get‑Service,

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Name and Exclude, and the values, as you can see,

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are also identical.

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And this splatting technique works whether the parameter is

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positional as name is or if it is required for you to type the

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name if you want to use it like exclude.

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So $p is a hashtable to name value pairs.

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The name matches the parameter name and the value

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matches the value that you want to give.

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So now what I can do is I can run Get‑Service and splat the hashtable.

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Now splatting, you can see I get the same result.

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The syntax is a little bit different.

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Pay close attention here.

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Notice I'm using the @ symbol and then the name of

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the variable that has my hashtable, $p.

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There is no dollar sign, it's just @p,

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and so it looks for key names that match up to your parameter names

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and then joins those things together and then everything runs the

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way that you would normally expect.

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Now a reason this is really useful,

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and this maybe something that's more important when you get to scripting,

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is you can rebuild these hashtables kind of on the fly.

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Now I'm going to do this in the console.

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Let's create another hashtable and this is a hashtable

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that I can use with Get‑CimInstance.

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Now in this particular hashtable,

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I'm using the ‑verbose parameter because that is a switch that I want to enable.

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In a hashtable, I'll use a value of $true, and there you can see the hashtable.

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So now I can run Get‑CimInstance and splat $cim.

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Notice again, @cim.

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I get the verbose output and you can see the results there.

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Now though, I can easily modify the hashtable.

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Let's say I want to get the win32 operating system.

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So if I just change the Classname parameter, everything else remains the same.

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And now I can rerun the command, again splatting,

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and I get a different result pretty much using the same hashtable.

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All I did was just change what needed to be changed.

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Again, when you get to scripting,

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I think this is a technique that you will be using often.

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If you need to though, you can also specify additional parameters.

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In this case,

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I'm combining the hashtable and then I'm also specifying

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an additional parameter ‑ComputerName.

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So now I'm acquiring a remote computer to get the operating system information.

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Again,

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this is something that you will likely use more when you get to scripting and there is a help topic that you should take a look at.