Change Data template for Sitecore Items while retaining data for existing fields

Recently, had to move a bucket of items from one template to another. I also thought this would be a classic case to showcase a scenario to migrate data from source to target fields since most of the fields were existing ones with just field name change. 

Source and target fields:

Source Field	Source Field Display Name	Target Field	Target Field Display Name	Field Type
Is Active	Is Active	IsActive	Is Active	Checkbox
Is Shown in Special Offers	Is Shown in Special Offers	IsShowninCurrentOffers	Is Showin in Current Offers	Checkbox
Regions	Regions	Regions	Regions	treelist
Disclaimers	Disclaimers	Disclaimers	Disclaimers	treelist
CTAs	CTAs	CTAs	CTAs	treelist
Offer Price	Offer Price	OfferPrice	Offer Price	Number
Sub Title	Sub Title	VehicleSubtitle	Vehicle Sub-title	Multiline text
Title	Title	VehicleTitle	Vehicle Title	Singleline text
Is Non Price Offer	Is Non-Price Offer	IsNonPriceOffer	Is Non-Price Offer	Checkbox
Material Codes	Material Code(s)	MaterialCodes	Material Code(s)	treelist

I just have a snapshot of the fields here in the table above. Even in the snapshot above, it can be noticed that some of the fields like "Is Active" if named without any spaces, there is no need to include them in the migration PS script (below) since they would map automatically and port data. 

So, It will be good to have Item names without spaces. Instead, go with the age-old convention of adding special characters and spaces to display name field since that is the reason for having the display name field. While item name without spaces can be useful while writing scripts.

Also, note that in the PS script below, the item names are NOT display names but the actual item names. So, ensure to pick up the item name when you write such scripts.

Finally, here is my PS script that changes the template and migrates the data:

########################################################

Write-Host "Start"

########################################################

$rootItem = Get-Item master:"/content/xyz/Main Site/test";

$sourceTemplate = Get-Item "{89FA35EA-F1DF-49DD-A429-FC39D015500C}";

$targetTemplate = Get-Item "{7977385E-3F2C-4FC3-9502-A95B43EF9A35}";

Get-ChildItem $rootItem.FullPath -recurse | Where-Object { $_.TemplateName -eq $sourceTemplate.Name } | ForEach-Object {

    $fieldVehicleGrade= $_."Vehicle Grade";

    $fieldAvailableExtras= $_."Available Extras";

    $fieldKeySellingFactors= $_."Key Selling Factors";

    $fieldVehicleVariant= $_."Vehicle Variant";

    $fieldMaterialCodes= $_."Material Codes";

    $fieldImageAlt= $_."Image Alt";

    $fieldOfferPrice= $_."Offer Price";

    $fieldTitle = $_."Title";

    $fieldSubTitle = $_."Sub Title";

    $fieldOverrideOfferPrice= $_."Override Offer Price";

    $fieldEnableOmnichannelIntegration= $_."Enable Omnichannel Integration";

    $fieldIsNonPriceOffer= $_."Is Non Price Offer";

    $fieldIsActive = $_."Is Active";

    $fieldTitle = $_."Title";

    $fieldSubTitle = $_."Sub Title";

    $fieldIsShowninSplOffers= $_."Is Shown in Special Offers";

    $fieldIsShownonPricingPage= $_."Is Shown on Pricing Page";    

    $_.ChangeTemplate($targetTemplate);

    $updatedItem = Get-Item $_.ID;    

    $updatedItem.VehicleTitle = $fieldTitle;    

    $updatedItem.VehicleSubTitle = $fieldSubTitle;    

    $updatedItem.VehicleGrade = $fieldVehicleGrade;

    $updatedItem.AvailableExtras = $fieldAvailableExtras;    

    $updatedItem.VehicleInclusions = $fieldKeySellingFactors;    

    $updatedItem.VehicleVariant = $fieldVehicleVariant;    

    $updatedItem.VehicleGrade = $fieldVehicleGrade;    

    $updatedItem.MaterialCodes = $fieldMaterialCodes;    

    $updatedItem.ImageAlt = $fieldImageAlt;    

    $updatedItem.OfferPrice = $fieldOfferPrice;    

    $updatedItem.IsNonPriceOffer = $fieldIsNonPriceOffer;    

    $updatedItem.OverrideOfferPrice = $fieldOverrideOfferPrice;    

    $updatedItem.VehicleVariant = $fieldVehicleVariant;    

    $updatedItem.IsShowninCurrentOffers = $fieldIsShowninSplOffers;    

    $updatedItem.IsShownonPricingrelatedModules = $fieldIsShownonPricingPage;    

    $updatedItem.IsActive = $fieldIsActive;

}

Write-Host "Done"

###############################################################

Also, notice how easy it is to add field names without spaces to the target $updatedItem variable in the above script. Also, on the right side, you can see the source field with spaces enclosed within double quotes. 

Most importantly, ensure to do an iisreset before running the script!