1 00:00:01,040 --> 00:00:04,600 Now let me show you a few other tricks here with hash tables. 2 00:00:04,600 --> 00:00:07,270 Let me create an array, $j, and just give it a single 3 00:00:07,270 --> 00:00:10,400 entry of name with the value of foo. 4 00:00:10,400 --> 00:00:10,730 Now, 5 00:00:10,730 --> 00:00:13,680 later on, I decide, you know what, I want to add another 6 00:00:13,680 --> 00:00:16,240 entry called name with the value of bar, 7 00:00:16,240 --> 00:00:19,720 maybe not realizing what I have already done. And PowerShell 8 00:00:19,720 --> 00:00:24,060 will complain because a hash table key has to be unique, and I 9 00:00:24,060 --> 00:00:25,680 already have an entry for name. 10 00:00:25,680 --> 00:00:28,670 One thing you can do is to test if the hash table already 11 00:00:28,670 --> 00:00:32,050 contains that key, and you can do that with a method of the 12 00:00:32,050 --> 00:00:36,040 hash table. So I pipe $j to Get‑Member. 13 00:00:36,040 --> 00:00:39,540 I know there are methods that have contains in the name. 14 00:00:39,540 --> 00:00:41,990 There's Contains, ContainsKey, which basically do the 15 00:00:41,990 --> 00:00:44,530 same thing, and then ContainsValue. 16 00:00:44,530 --> 00:00:47,130 These will give you a boolean result, 17 00:00:47,130 --> 00:00:52,610 basically true or false, if the key exists or if the value already exists in 18 00:00:52,610 --> 00:00:59,870 the hash table. So I can do $j.ContainsKey('name'), and sure enough, it does, 19 00:00:59,870 --> 00:01:02,810 and I'll get the same result if I use Contains. 20 00:01:02,810 --> 00:01:05,410 So here's how we might use this in a more practical 21 00:01:05,410 --> 00:01:09,950 perspective. I'm going to run Get‑Process. And for every 22 00:01:09,950 --> 00:01:13,100 process object that comes through the pipeline, 23 00:01:13,100 --> 00:01:17,790 I'm going to do something. Now before I do something, 24 00:01:17,790 --> 00:01:20,490 I'm going to initialize an empty hash table, 25 00:01:20,490 --> 00:01:22,940 $p. 26 00:01:22,940 --> 00:01:25,160 Now as every object comes through the pipeline, 27 00:01:25,160 --> 00:01:26,610 I'm first going to test, hey, 28 00:01:26,610 --> 00:01:33,140 does $p already contain an entry using the name of the process as the key? 29 00:01:33,140 --> 00:01:34,260 If it does, 30 00:01:34,260 --> 00:01:38,550 then I'm going to update the value with the working 31 00:01:38,550 --> 00:01:40,470 set value of the current process. 32 00:01:40,470 --> 00:01:45,440 I'm using the += sign to increment and update the value. 33 00:01:45,440 --> 00:01:51,930 So the hash table will have a key for the process name, and the value will be 34 00:01:51,930 --> 00:01:59,240 the sum of the working set value of the process object. 35 00:01:59,240 --> 00:02:04,460 Otherwise, if $p does not contain the name of the process, 36 00:02:04,460 --> 00:02:08,440 then I will just go ahead and add it to the hash table and then add 37 00:02:08,440 --> 00:02:13,440 the current working set to my starting point. 38 00:02:13,440 --> 00:02:17,670 So when I run this, $p now has this information. I have the 39 00:02:17,670 --> 00:02:20,920 process name and then the working set size. 40 00:02:20,920 --> 00:02:24,830 So using that contains method allowed me to nicely and 41 00:02:24,830 --> 00:02:29,940 easily update the hash table as I needed to. 42 00:02:29,940 --> 00:02:33,540 Now here's, though, another place where something may trip you up. 43 00:02:33,540 --> 00:02:35,350 I then decide, you know what, I want to sort that 44 00:02:35,350 --> 00:02:38,540 output on the name of the process. 45 00:02:38,540 --> 00:02:41,540 So we try something like that, and we go, hey, that did not work. 46 00:02:41,540 --> 00:02:45,440 This is where things like Get‑Member become very important. 47 00:02:45,440 --> 00:02:50,890 If I take $p and pipe it to Get‑Member, you can see that PowerShell is getting 48 00:02:50,890 --> 00:02:56,160 a System.Collection.Hashtable object from $p. It's not a process object, and 49 00:02:56,160 --> 00:03:01,960 it's not the entry for the process object, so it doesn't know about that name 50 00:03:01,960 --> 00:03:07,300 property. We can see it's not listed there. Instead, what you need to do is do 51 00:03:07,300 --> 00:03:10,940 something called GetEnumerator. 52 00:03:10,940 --> 00:03:12,840 So I'm going to take GetEnumerator. 53 00:03:12,840 --> 00:03:15,140 This is a method on the hash table. 54 00:03:15,140 --> 00:03:18,130 If I pipe this to Get‑Member to show you, you can see 55 00:03:18,130 --> 00:03:20,040 now this is a different object type, 56 00:03:20,040 --> 00:03:26,040 a System.Collections.DictionaryEntry. And look at the properties, Key and Value. 57 00:03:26,040 --> 00:03:29,040 And I believe starting in PowerShell 7, they added an 58 00:03:29,040 --> 00:03:31,910 AliasProperty of Name for the Key. 59 00:03:31,910 --> 00:03:37,740 Now what you need to do is this, so I take $p GetEnumerator. I can 60 00:03:37,740 --> 00:03:42,770 still use my Sort‑Object, but the property that I want is Name or Key 61 00:03:42,770 --> 00:03:44,550 if I want to use the actual value. Here, 62 00:03:44,550 --> 00:03:47,940 I'm just using the AliasProperty. 63 00:03:47,940 --> 00:03:52,100 Now I get the results that I expect, and it sorts the way that I expect 64 00:03:52,100 --> 00:03:56,610 because I'm using the proper property name now that I know what type of 65 00:03:56,610 --> 00:04:00,740 object PowerShell is getting in the pipeline. 66 00:04:00,740 --> 00:04:05,020 I can do $p GetEnumerator and filter and say, hey, get me all the 67 00:04:05,020 --> 00:04:09,730 ones where the value is greater than 250 megabytes. And see, I've got 68 00:04:09,730 --> 00:04:14,590 one entry listed there. So knowing how to use GetEnumerator is 69 00:04:14,590 --> 00:04:18,290 important. If you are using a hash table and you're not getting the 70 00:04:18,290 --> 00:04:25,000 results you are expecting, it may be because you need to use this GetEnumerator method.