Use StringBuilder to combine multiple strings

$stringBuilder = New-Object System.Text.StringBuilder
for ($i = 0; $i -lt 10; $i++){
    $stringBuilder.Append("Line $i`r`n") | Out-Null
}
$stringBuilder.ToString()

Details

This performs much better the stanard array builder of +=

Example

PS C:\> $stringBuilder = New-Object System.Text.StringBuilder
>> for ($i = 0; $i -lt 10; $i++){
>>     $stringBuilder.Append("Line $i`r`n") | Out-Null
>> }
>> $stringBuilder.ToString()

Line 0
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9