How can I edit rendering parameters programatically?

Question

I have a rendering that is used on pages all over my site, and I had to add a new field to the Rendering Parameters it uses. I now need to update this field on a huge number of renderings, but only on renderings that exist within a particular placeholder, so I can't just apply it globally in standard values.

I've started writing a script to update the rendering parameters, and I think I've got the code to retrieve and modify the rendering parameters, but I'm not sure how to apply it back to the rendering and save it.

var testPage = db.GetItem("/sitecore/content/Home/Magazine/Issues/2009/August");
var renderings = testPage.Visualization.GetRenderings(Sitecore.Context.Device, true);

foreach (var rendering in renderings)
{
    var placeholderId = rendering.Placeholder;

    // check renderingitem id
    if (rendering.RenderingItem.ID == new Sitecore.Data.ID("{93F07F46-F356-419A-B937-A5EB2A9D63DD}"))
    {

        if (placeholderId == "/content-body/secondary-column-left")
        {

            var parameterString = rendering.RenderingItem.Parameters;
            var parameters = HttpUtility.ParseQueryString(parameterString);
            parameters["Display Subtitle"] = "1";
            parameterString = parameters.ToString();

            // HOW DO I PUT THIS BACK ON THE RENDERING NOW?
        }
    }
}

Answer 1

Got the answer, here is the complete code. In my case I'm updating the Display Subtitle field but you can change this field or make the field name a variable if you want to:

public void SetRenderingParameterValue(
    Item item)
{
    using (new SecurityDisabler())
    {
        string defaultDeviceId = "{FE5D7FDF-89C0-4D99-9AA3-B5FBD009C9F3}";
        string dynamicContentListingRenderingId = "{93F07F46-F356-419A-B937-A5EB2A9D63DD}";

        var layoutField = new LayoutField(item.Fields[Sitecore.FieldIDs.LayoutField]);
        var layoutDefinition = LayoutDefinition.Parse(layoutField.Value);
        var deviceDefinition = layoutDefinition.GetDevice(defaultDeviceId);
        foreach (RenderingDefinition rendering in deviceDefinition.Renderings)
        {
            var datasource = rendering.Datasource;
            var placeholderId = rendering.Placeholder;

            if (placeholderId == "/content-body/secondary-column-left")
            {
                if (rendering != null && rendering.ItemID == dynamicContentListingRenderingId)
                {
                    var parameters = HttpUtility.ParseQueryString(rendering.Parameters);
                    parameters.Remove("Display Subtitle");
                    parameters["Display Subtitle"] = "1";
                    var newParams = HttpUtility.UrlDecode(parameters.ToString());
                    rendering.Parameters = newParams;
                }
            }
        }
        item.Editing.BeginEdit();
        item[Sitecore.FieldIDs.LayoutField] = layoutDefinition.ToXml();
        item.Editing.EndEdit();

    }
}

The defaultDeviceId is the ID of /sitecore/layout/Devices/Default (or whatever Device your rendering is on)

dynamicContentListingRenderingId is the ID of my rendering item under /sitecore/layout/Renderings

Answer 2

I've not completely test this using Sitecore PowerShell Extensions, but it should get you pretty close.

$item = Get-Item -Path "master" -ID "{961563FC-3445-4558-BF3A-06DF06BA6298}"
$renderingItemId = "{93F07F46-F356-419A-B937-A5EB2A9D63DD}"
$placeholderId = "/content-body/secondary-column-left"

# Accepts Hashtable, Ordered Dictionaries, etc.
$parameters = [ordered]@{"Display Subtitle"="1"}
Get-Rendering -Item $item -FinalLayout |
    Where-Object { $_.Placeholder -eq $placeholderId -and $_.ItemID -eq $renderingItemId } |
    Set-RenderingParameter -Parameter $parameters | 
    Set-Rendering -Item $item -FinalLayout