tfs.work.item.lib.psm1

[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.TeamFoundation.Client")
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.TeamFoundation.WorkItemTracking.Client")
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.TeamFoundation.Build.Client")
Add-PSSnapin Microsoft.TeamFoundation.PowerShell

Function Get-WorkitemFieldValue([string]$TFSURL, [string]$WorkitemId, [string]$FieldName)
{
    $teamProjectCollection = [Microsoft.TeamFoundation.Client.TfsTeamProjectCollectionFactory]::GetTeamProjectCollection($TFSURL)
    $wit = $teamProjectCollection.GetService([Type]"Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore")
    $items = $wit.GetWorkItem($WorkitemId)
    $value = $items.Fields[$FieldName].Value
    return $value
}

Function Update-WorkitemField([string]$TFSURL, [string]$WorkitemId, [string]$FieldName, $FieldValue)
{
    $teamProjectCollection = [Microsoft.TeamFoundation.Client.TfsTeamProjectCollectionFactory]::GetTeamProjectCollection($TFSURL)
    $wit = $teamProjectCollection.GetService([Type]"Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore")
    $items = $wit.GetWorkItem($WorkitemId)
    Write-Host "Before change, $FieldName is $($items.Fields[$FieldName].Value)"
    $items.Fields[$FieldName].Value = $FieldValue
    $wit.BatchSave($items)
}

Function Append-WorkitemField([string]$TFSURL, [string]$WorkitemId, [string]$FieldName, [string]$TextString)
{
    $val = Get-WorkitemFieldValue $TFSURL $WorkitemId $FieldName
    $val += $TextString
    Update-WorkitemField $TFSURL $WorkitemId $FieldName $val
}

Function QueryAndBulkEdit([string]$TFSURL, [string]$FieldNameForPath, [string]$WorkItemPath, [string]$FieldName, [string]$SearchString, [string]$FieldNameForUpdate, [string]$UpdateValue)
{
    $teamProjectCollection = [Microsoft.TeamFoundation.Client.TfsTeamProjectCollectionFactory]::GetTeamProjectCollection($TFSURL)
    $wit = $teamProjectCollection.GetService([Type]"Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemStore")

    $WIQL = @"
    SELECT [System.Id], [System.WorkItemType], [System.State], [System.AssignedTo], [System.Title] 
    FROM WorkItems 
    WHERE [System.$FieldNameForPath] = '$WorkItemPath' AND [System.$FieldName] Contains '$SearchString'
    ORDER BY [System.WorkItemType], [System.Id] 
    "@

    Write-Host $WIQL
    $collection = $wit.Query($WIQL) 
    foreach($item in $collection)
    {
        Write-Host "Update $($item.Id) $FieldNameForUpdate Field with $UpdateValue"
        Update-WorkitemField $TFSURL $item.Id $FieldNameForUpdate $UpdateValue
    }
}