Teamcity powershell task to output current build number, date, and svn rev in JSON to 'build.json' in root.

gistfile1.ps1

Add-Type -Assembly System.ServiceModel.Web,System.Runtime.Serialization
function Read-Stream {
PARAM(
   [Parameter(Position=0,ValueFromPipeline=$true)]$Stream
)
process {
   $bytes = $Stream.ToArray()
   [System.Text.Encoding]::UTF8.GetString($bytes,0,$bytes.Length)
}}

function New-Json {
[CmdletBinding()]
param([Parameter(ValueFromPipeline=$true)][HashTable]$InputObject) 
begin { 
   $ser = @{}
   $jsona = @()
}
process {
   $jsoni = 
   foreach($input in $InputObject.GetEnumerator() | Where { $_.Value } ) {
      if($input.Value -is [Hashtable]) {
         '"'+$input.Key+'": ' + (New-JSon $input.Value)
      } else {
         $type = $input.Value.GetType()
         if(!$Ser.ContainsKey($Type)) {
            $Ser.($Type) = New-Object System.Runtime.Serialization.Json.DataContractJsonSerializer $type
         }
         $stream = New-Object System.IO.MemoryStream
         $Ser.($Type).WriteObject( $stream, $Input.Value )
         '"'+$input.Key+'": ' + (Read-Stream $stream)
      }
   }

   $jsona += "{`n" +($jsoni -join ",`n")+ "`n}"
}
end { 
   if($jsona.Count -gt 1) {
      "[$($jsona -join ",`n")]" 
   } else {
      $jsona
   }
}}
$date=(Get-Date).ToUniversalTime().ToString("yyyy-MM-dd HH:mm:ss");
@{BuildNumber="%build.number%"; SvnRevision="%env.BUILD_VCS_NUMBER%"; BuildTime=$date} | New-Json > build.json