LANCommander/LANCommander.PowerShell/Cmdlets/Write-ReplaceContentInFile.cs

using System.IO;
using System.Management.Automation;
using System.Text.RegularExpressions;

namespace LANCommander.PowerShell.Cmdlets
{

    [Cmdlet(VerbsCommunications.Write, "ReplaceContentInFile")]
    [OutputType(typeof(string))]
    public class ReplaceContentInFileCmdlet : Cmdlet
    {
        [Parameter(Mandatory = true, Position = 0)]
        public string Pattern { get; set; }

        [Parameter(Mandatory = true, Position = 1)]
        public string Substitution { get; set; }

        [Parameter(Mandatory = true, Position = 2)]
        public string FilePath { get; set; }

        protected override void ProcessRecord()
        {
            if (File.Exists(FilePath))
            {
                var contents = File.ReadAllText(FilePath);
                var regex = new Regex(Pattern, RegexOptions.Multiline);

                contents = regex.Replace(contents, Substitution);

                File.WriteAllText(FilePath, contents);

                WriteObject(contents);
            }
        }
    }
}