How can you get a unique ID for a rendering on a specific Sitecore item?

Question

I need to programmatically update all of the instances of a particular rendering attached to a Sitecore item.

This is the code I first tried and failed to use:

foreach (RenderingReference renderingReference in parentRenderingReferences)
{
    /* ... unrelated code removed ... */
    var layoutField = new LayoutField(contentItem.Fields[FieldIDs.LayoutField]);
    LayoutDefinition layoutDef = LayoutDefinition.Parse(layoutField.Value);
    DeviceDefinition deviceDef = layoutDef.GetDevice(device.ID.ToString());

    // Update the rendering's datasource
    RenderingDefinition renderingDefinition =
        deviceDef.GetRendering(renderingReference.RenderingID);
    renderingDefinition.Datasource = newDataSourceValue;
    /* ... unrelated code removed ... */
}

Using RenderingReference.RenderingID in the final statement in that code didn't work, as the RenderingID is the ID of the actual rendering item that lives in /layouts/renderings. So if the item has more than one of the same rendering on a template the code never accesses any renderings after the first instance. I tried using RenderingReference.UniqueID, which appeared to be what I was looking for (the ID of the instance of the rendering):

foreach (RenderingReference renderingReference in parentRenderingReferences)
{
    /* ... unrelated code removed ... */
    var layoutField = new LayoutField(contentItem.Fields[FieldIDs.LayoutField]);
    LayoutDefinition layoutDef = LayoutDefinition.Parse(layoutField.Value);
    DeviceDefinition deviceDef = layoutDef.GetDevice(device.ID.ToString());

    // Update the rendering's datasource
    RenderingDefinition renderingDefinition =
        deviceDef.GetRendering(renderingReference.UniqueID);
    renderingDefinition.Datasource = newDataSourceValue;
    /* ... unrelated code removed ... */
}

In this case, the resulting renderingDefinition object is null, so that doesn't work either.

Answer 1

The solution that ended up working for me was to use the DeviceDefinition.GetRenderingByUniqueId method with the RenderingReference.UniqueID object:

foreach (RenderingReference renderingReference in parentRenderingReferences)
{
    /* ... unrelated code removed ... */
    var layoutField = new LayoutField(contentItem.Fields[FieldIDs.LayoutField]);
    LayoutDefinition layoutDef = LayoutDefinition.Parse(layoutField.Value);
    DeviceDefinition deviceDef = layoutDef.GetDevice(device.ID.ToString());

    // Update the rendering's datasource
    RenderingDefinition renderingDefinition =
        deviceDef.GetRenderingByUniqueId(renderingReference.UniqueID);
    renderingDefinition.Datasource = newDataSourceValue;
    /* ... unrelated code removed ... */
}