How do I insert text after a specific line in files using powershell?

As part of a huge refactoring I removed some duplicate classes and enums. I moved namespaces and restructured everything to be easier to maintain in the future.

All changes has been scripted already except for one thing. I need to insert a data contract namespace in every file that uses another namespace if the data contract namespace has not been inserted yet.

The code I have at the moment does not work but is sort of what I need I guess.

function Insert-Usings{
    trap {
        Write-Host ("ERROR: " + $_) -ForegroundColor Red
        return $false 
    }
    (Get-ChildItem $base_dir -Include *.asmx,*.ascx,*.cs,*.aspx -Force -Recurse -ErrorAction:SilentlyContinue) | % {
    $fileName  = $_.FullName
    (Get-Content $fileName) | 
        Foreach-Object 
        {
            $_
            if ($_ -cmatch "using Company.Shared;") { 
                    $_ -creplace "using Company.Shared;", "using Company.Common;"
            }
  开发者_运维问答          elseif ($_ -cmatch "using Company") {
                #Add Lines after the selected pattern 
                "using Company.Services.Contracts;"
            }
            else{
                $_
            }
        }
    } | Set-Content $fileName
}

Edit: The code tends to output (overwrite the whole file with-) "using Company.Services.Contracts" statements.

It is not quite clear what you what to get exactly but I'll try to guess, see my comments in the code. The original code, I think, contains a few mistakes, one is serious: Set-Content is used in a wrong pipeline/loop. Here is the corrected code.

function Insert-Usings
{
    trap {
        Write-Host ("ERROR: " + $_) -ForegroundColor Red
        return $false
    }
    (Get-ChildItem $base_dir -Include *.asmx,*.ascx,*.cs,*.aspx -Force -Recurse -ErrorAction:SilentlyContinue) | % {
        $fileName  = $_.FullName
        (Get-Content $fileName) | % {
            if ($_ -cmatch "using Company\.Shared;") {
                # just replace
                $_ -creplace "using Company\.Shared;", "using Company.Common;"
            }
            elseif ($_ -cmatch "using Company") {
                # write the original line
                $_
                # and add this after
                "using Company.Services.Contracts;"
            }
            else{
                # write the original line
                $_
            }
        } |
        Set-Content $fileName
    }
}

For example, it replaces this:

xxx

using Company.Shared;

using Company;

ttt

with this:

xxx

using Company.Common;

using Company;
using Company.Services.Contracts;

ttt

Note: presumably you should not apply this code to sources more than once, the code is not designed for this.