String concatenation performance boosting

String concatenation performance boosting - is this too much ado about nothing?

Concatenating strings is a common operation in programming, but did you know that there are different methods you can use to do it? In this post, we will explore four popular methods for string concatenation in PowerShell and compare their performance.

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The Methods

The four methods we will focus on are:

• += operator
• -join operator
• [string]::Concat() method
• StringBuilder class with the .append() method

To test these methods, we will generate a 9-character long string by randomly selecting characters between ASCII codes 65 and 90, and then concatenate this string 10,000 times. We will time each method and compare their performance. Here's the code we'll use to generate the strings:

$((0..8).foreach({
        [char]$(Get-Random -Minimum 65 -Maximum 90)
}) -join "")

---

The Test

#classic += method
$Superlongstring = [string]::empty
$StopWatch = New-Object System.Diagnostics.Stopwatch
$StopWatch.Start()
(0..10000).foreach({
    $Superlongstring +=$((0..8).foreach({
        [char]$(Get-Random -Minimum 65 -Maximum 90)
    }) -join "")
})
$StopWatch.Stop()
$TestList.add([PSCustomObject]@{
    Method = "+= method"
    TimeElapsed = $StopWatch.Elapsed
    TimeElapsedMS = $StopWatch.ElapsedMilliseconds
})

#join string method
$Superlongstring = [string]::empty
$StopWatch = New-Object System.Diagnostics.Stopwatch
$StopWatch.Start()
(0..10000).foreach({
    $Superlongstring = -join($Superlongstring,$((0..8).foreach({
        [char]$(Get-Random -Minimum 65 -Maximum 90)
    })))
})
$StopWatch.Stop()
$TestList.add([PSCustomObject]@{
    Method = "-join method"
    TimeElapsed = $StopWatch.Elapsed
    TimeElapsedMS = $StopWatch.ElapsedMilliseconds
})

#string concat method
$Superlongstring = [string]::empty
$StopWatch = New-Object System.Diagnostics.Stopwatch
$StopWatch.Start()
(0..10000).foreach({
    $Superlongstring = [string]::Concat($Superlongstring,$((0..8).foreach({
        [char]$(Get-Random -Minimum 65 -Maximum 90)
    }) -join ""))
})
$StopWatch.Stop()
$TestList.add([PSCustomObject]@{
    Method = "string concat method"
    TimeElapsed = $StopWatch.Elapsed
    TimeElapsedMS = $StopWatch.ElapsedMilliseconds
})

#stringbuilder class method
$Superlongstring =  [System.Text.StringBuilder]::new()
$StopWatch = New-Object System.Diagnostics.Stopwatch
$StopWatch.Start()
(0..10000).foreach({
    $Superlongstring.append($((0..8).foreach({
        [char]$(Get-Random -Minimum 65 -Maximum 90)
    }) -join "")) | Out-Null
})
$Superlongstring = $Superlongstring.tostring()
$StopWatch.Stop()
$TestList.add([PSCustomObject]@{
    Method = "stringbuilder class method"
    TimeElapsed = $StopWatch.Elapsed
    TimeElapsedMS = $StopWatch.ElapsedMilliseconds
})

---

The Results

After running the test, we get the following results:

Method	TimeElapsed	TimeElapsedMS
+= method	00:00:02.9537727	2953
-join method	00:00:04.5625753	4562
string concat method	00:00:05.0997880	5099
stringbuilder class method	00:00:02.4714697	2471

---

The Conclusion

The second fastest method was the += operator, but the fastest was the StringBuilder class with the .append() method. It's worth noting that with the StringBuilder method, we needed to convert the object back to a string using the .ToString() method, but even with this additional step, it was still faster than the other methods.

If you have any thoughts or feedback on this topic, feel free to share them with me on Twitter at Christian Ritter.

All tests were conducted using PowerShell 7.x.

Best regards,

Christian.