Question

Using this code I managed to change the renderings on the current item. However this changed it permenantly in Sitecore (the changes were could be seen in the CMS) and not temporarily, as I expected.

void ReplaceLayout(Item item)
{
    if (item == null)
        return;

    using (new SecurityDisabler())
    {
        // New item
        LayoutField newLayoutField = new LayoutField(item.Fields[Sitecore.FieldIDs.LayoutField]);
        LayoutDefinition newLayoutDefinition = LayoutDefinition.Parse(newLayoutField.Value);

        DeviceDefinition newDeviceDefinition = newLayoutDefinition.GetDevice(Sitecore.Context.Device.ID.ToString());

        // Current item
        LayoutField layoutField = new LayoutField(Sitecore.Context.Item.Fields[Sitecore.FieldIDs.LayoutField]);
        LayoutDefinition layoutDefinition = LayoutDefinition.Parse(layoutField.Value);

        DeviceDefinition deviceDefinition = layoutDefinition.GetDevice(Sitecore.Context.Device.ID.ToString());
        deviceDefinition.Layout = newDeviceDefinition.Layout;
        deviceDefinition.Renderings = newDeviceDefinition.Renderings;

        Sitecore.Context.Item.Editing.BeginEdit();
        layoutField.Value = layoutDefinition.ToXml();
        Sitecore.Context.Item.Editing.EndEdit();
    }
}

I don’t want to make permenant changes to the item, I just want to replace the currently displayed items renderings on the fly if some conditions are met. Does anyone know how to alter an item’s layout in this way?

Answer 1

You explained in your comments that you want to display certain sublayouts in the sidebar depending on certain form parts/steps.
You can do that by adding a PlaceHolder that will fit the sublayouts (e.g. in your sidebar) and use this code to dynamically render sublayouts to it.

First you need an item (i call it a snippet item) that has the sublayout configured on its presentation settings.
Then you can use code to render that item inside the placeholder (phSideBarPlaceHolder).

// Load snippet item
Item snippet = Sitecore.Context.Database.GetItem("{id-or-path-of-snippet-item}");

// Get the first rendering from item's presentation definition
RenderingReference rendering = snippet.Visualization.GetRenderings(Sitecore.Context.Device, false).FirstOrDefault();

// We assume that its a Sublayout, but you can also check for xslt and create an XslFile() object
Sublayout sublayout = new Sublayout();
sublayout.DataSource = snippet.Paths.FullPath; // creates a reference to the snippet item, so you can pull data from that later on
sublayout.Path = rendering.RenderingItem.InnerItem["Path"];
sublayout.Cacheable = rendering.RenderingItem.Caching.Cacheable;

// Copy cache settings
if (rendering.RenderingItem.Caching.Cacheable)
{
    sublayout.VaryByData = rendering.RenderingItem.Caching.VaryByData;
    sublayout.VaryByDevice = rendering.RenderingItem.Caching.VaryByDevice;
    sublayout.VaryByLogin = rendering.RenderingItem.Caching.VaryByLogin;
    sublayout.VaryByParm = rendering.RenderingItem.Caching.VaryByParm;
    sublayout.VaryByQueryString = rendering.RenderingItem.Caching.VaryByQueryString;
    sublayout.VaryByUser = rendering.RenderingItem.Caching.VaryByUser;
}

// Now render the sublayout to the placeholder
phSideBarPlaceHolder.Controls.Add(sublayout);

If you need more info about how to read data the DataSource property inside the sublayout code, Mark Ursino has written an article about that: http://firebreaksice.com/using-the-datasource-field-with-sitecore-sublayouts