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Customize a SharePoint page by using remote provisioning and CSS

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You can use cascading style sheets (CSS) to customize SharePoint rich text fields and web part zones. To customize rich text fields, you can do this right on the page you're editing. For web part zones, you can use the Script Editor web part to add HTML or scripts, or associate a CSS style sheet.

For a code sample that is associated with this article, see Branding.AlternateCSSAndSiteLogo in the Office 365 Developer Patterns and Practices project on GitHub.

Important

This extensibility option is only available for classic SharePoint experiences. You cannot use this option with modern experiences in SharePoint Online, like with communication sites. Notice also that you should not take a dependency on the html page structure or on the out-of-the-box CSS style names as these might be adjusted without a notice.

Customize rich text fields

You can customize rich text fields by using CSS right in the page editor:

  1. On your SharePoint page, choose Edit to open the page editor.

  2. From the ribbon, choose Insert > Embed Code.

You can now add or modify CSS elements for a rich text field.

Customize web part zones

To customize web part zones by using CSS, you use the Script Editor web part.

Note

If you are using SharePoint Online and the NoScript feature, the Script Editor web part is disabled.

The following code example uploads custom CSS to the Asset Library, applies a reference to the CSS URL with a custom action, and then creates a custom action to build a link to the new CSS file.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using Microsoft.SharePoint.Client;
using Microsoft.SharePoint.Client.EventReceivers;

namespace AlternateCSSAppAutohostedWeb.Services
{
    public class AppEventReceiver : IRemoteEventService
    {
        public SPRemoteEventResult ProcessEvent(SPRemoteEventProperties properties)
        {
            SPRemoteEventResult result = new SPRemoteEventResult();

            try
            {
                using (ClientContext clientContext = TokenHelper.CreateAppEventClientContext(properties, false))
                {
                    if (clientContext != null)
                    {
                        Web hostWebObj = clientContext.Web;

                        List assetLibrary = hostWebObj.Lists.GetByTitle("Site Assets");
                        clientContext.Load(assetLibrary, l => l.RootFolder);

                        // First, upload the CSS files to the Asset Library.
                        DirectoryInfo themeDir = new DirectoryInfo(System.Web.Hosting.HostingEnvironment.ApplicationPhysicalPath + "CSS");
                        foreach (var themeFile in themeDir.EnumerateFiles())
                        {
                            FileCreationInformation newFile = new FileCreationInformation();
                            newFile.Content = System.IO.File.ReadAllBytes(themeFile.FullName);
                            newFile.Url = themeFile.Name;
                            newFile.Overwrite = true;

                            Microsoft.SharePoint.Client.File uploadAsset = assetLibrary.RootFolder.Files.Add(newFile);
                            clientContext.Load(uploadAsset);
                            break;
                        }
                        
                        string actionName = "SampleCSSLink";

                        // Now, apply a reference to the CSS URL via a custom action.
                        
                        // Clean up existing actions that we may have deployed.
                        var existingActions = hostWebObj.UserCustomActions;
                        clientContext.Load(existingActions);

                        // Run uploads and initialize the existing Actions collection.
                        clientContext.ExecuteQuery();

                        // Clean up existing actions.
                        foreach (var existingAction in existingActions)
                        {
                            if(existingAction.Name.Equals(actionName, StringComparison.InvariantCultureIgnoreCase))
                                existingAction.DeleteObject();
                        }
                        clientContext.ExecuteQuery();

                        // Build a custom action to write a link to your new CSS file.
                        UserCustomAction cssAction = hostWebObj.UserCustomActions.Add();
                        cssAction.Location = "ScriptLink";
                        cssAction.Sequence = 100;
                        cssAction.ScriptBlock = @"document.write('<link rel=""stylesheet"" href=""" + assetLibrary.RootFolder.ServerRelativeUrl + @"/cs-style.css"" />');";
                        cssAction.Name = actionName;
                        
                        // Apply.
                        cssAction.Update();
                        clientContext.ExecuteQuery();
                    }
                    result.Status = SPRemoteEventServiceStatus.Continue;
                    return result;
                }
            }
            catch (Exception ex)
            {
                result.Status = SPRemoteEventServiceStatus.CancelWithError;
                result.ErrorMessage = ex.Message;
                return result;
            }
            
        }

        public void ProcessOneWayEvent(SPRemoteEventProperties properties)
        {
            // This method is not used by app events.
        }
    }
}

See also