File Name Contains Certain Text - powershell

Question

I know this is a new guy question, but I cant find anything. I think the issue might have to do with variable type issue?
I'm trying to look at a files name and see if pattern1 is contained in the file name. If so then replace the pattern text with "TEST".
Right now it doesn't error out, but it skips the IF, I do have files with the pattern in the directory.
Can't insert actually code, so here is a sample
$pattern1 = "January"
$pattern2 = "December 31"
$path = "C:\Users\...\METRICS-TEST\Metrics 2014\January 2014 Client Metrics"
$search_results = Get-ChildItem -Path $path | Where-Object { ((! $_.PSIsContainer))}
foreach ($file in $search_results) {
if($file.Name -contains $pattern1){
$new_name = $file.Name -replace $pattern1, "TEST1"
Rename-Item -Path $file.FullName -NewName $new_name
}else{
$new_name = $file.Name -replace $pattern2, "TEST2"
Rename-Item -Path $file.FullName -NewName $new_name
}
}

Answer 1

-contains work on collections, not strings.
For strings, you'd want either -match (for RegEx matching) or -like for simple wildcard matching:
$file.name -match $pattern1
$file.name -like "*$pattern1*"
-contains would be appropriate if you had an array of strings and wanted to know if it contained one or more copies of a specific string:
$Strings = "abc","def","ghi","jkl"
# This evaluates to true
$Strings -contains "abc"
# This evaluates to false
$Strings -contains "ab"

Answer 2

The whole issue is that you use -Contains where you should use -Match. Try this though, it's easily expandable if you have more conditions to add:
$pattern1 = "January"
$pattern2 = "December 31"
$path = "C:\Users\...\METRICS-TEST\Metrics 2014\January 2014 Client Metrics"
Switch(Get-ChildItem -Path $path){
{$_.Name -match $pattern1}{$new_name = $_.Name -replace $pattern1, "TEST1"
Rename-Item -Path $_.FullName -NewName $new_name}
{$_.Name -match $pattern2}{$new_name = $_.Name -replace $pattern2, "TEST2"
Rename-Item -Path $_.FullName -NewName $new_name}
}

Answer 3

I realize I have an accepted answer, but I thought another elegant way to handle this would be mapping Old-To-New in a hashtable, matching against the keys of that hashtable (regex escaped and joined with pipes to form the regex match pattern), and then renaming in a ForEach against the matches rather than a switch. I suppose at this point it's all academic.
$path = "C:\Users\...\METRICS-TEST\Metrics 2014\January 2014 Client Metrics"
$RenameMap = #{
"January" = "Test1"
"December 31" = "Test2"
}
$Pattern = "($(($RenameMap.keys|ForEach{[regex]::Escape($_)}) -join "|"))"
Get-ChildItem $Path | Where{$_.Name -match $Pattern} | ForEach {Rename-Item $_.FullName -NewName ($_.Name -Replace $Matches[1],$RenameMap[$Matches[1]])}