Umbraco Content Guid

Test.cs

// for document
var udi = new GuidUdi("document", myCurrentNode.GetGuid());

// for media
var image = UmbracoHelperContext.TypedMedia(1100);
var udi = new GuidUdi("media", image.GetGuid());

// using content service to update images field
product.SetValue("images", udi.ToString());

UmbracoContentGuid.cs

using System;
using Umbraco.Core;
using Umbraco.Core.Models;
using Umbraco.Core.Models.PublishedContent;
using Umbraco.Web;


public static Guid GetGuid(this IPublishedContent content)
{
    var contentWithKey = content as IPublishedContentWithKey;
    if (contentWithKey != null)
        return contentWithKey.Key;
    if (content is PublishedContentWrapped)
    {
        contentWithKey = ((PublishedContentWrapped)content).Unwrap() as IPublishedContentWithKey;
        if (contentWithKey != null)
            return contentWithKey.Key;
    }
    return Guid.Empty;
}

/// <summary>
/// Gets the published content with a guaranteed key
/// </summary>
/// <param name="content">The published content</param>
/// <returns>A published content with key</returns>
public static IPublishedContentWithKey GetContentWithKey(this IPublishedContent content)
{
    var withKey = content as IPublishedContentWithKey;

    if (withKey != null)
        return withKey;

    var wrapped = content as PublishedContentWrapped;

    if (wrapped != null)
        return GetContentWithKey(wrapped.Unwrap());

    return null;
}

/// <summary>
/// Guaranteed to return a GUID
/// </summary>
/// <param name="content">The published content</param>
/// <returns>A Guid</returns>
public static Guid GetKeyGuaranteed(this IPublishedContent content)
{
    var contentWithKey = content.GetContentWithKey();
    return contentWithKey != null ? contentWithKey.GetKey() : Guid.Empty;
}

/// <summary>
/// Gets an Umbraco UDI
/// </summary>
/// <param name="content">The published content</param>
/// <param name="objectType">The type of UDI to create</param>
/// <returns>An Umbraco Document Identifier</returns>
public static Udi GetUdi(this IPublishedContent content, UmbracoObjectTypes objectType)
{
    string type = Constants.UdiEntityType.FromUmbracoObjectType(objectType);
    return Udi.Create(type, content.GetKeyGuaranteed());
}