** Code for retrieving Audit History in MSCRM **

/** Code for retrieving Audit History in Microsoft Dynamics CRM 2011 **/

For retrieving from the Audit history we need to use “RetrieveRecordChangeHistoryResponse”.
The following sample (which I partially found something similar in the SDK) retrieves the information of the Audit history for any object in CRM

Create Organization Service Proxy

        static void Main(string[] args)
        {

            try
            {
               //Grab the organization service url by navigating to
               // Settings -> Customizations - > Developer Resources
               // CrmInstance.CrmServer URL for your CRM
               //CrmInstance.cc create a new ClientCredentials and pass your user name/password and domain
             using (var XrmProxy = new OrganizationServiceProxy(new Uri(CrmInstance.CrmServer + "/XRMServices/2011/Organization.svc"), null, CrmInstance.cc, null))
                {
                    ExtractFromAudit(XrmProxy);
                    Console.WriteLine("Thank you for participating in this amazing experiment! muwhaha!");
                    Console.ReadLine();
                 }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
                Console.ReadKey(true);
            }
        }

ExtractFromAudit Method

        private static void ExtractFromAudit(OrganizationServiceProxy XrmProxy)
        {
            // The GUID of the object you want to retirve in this case i am passing contactid
            var entityId = new Guid("4DC98353-CF88-E011-87E1-005056B30007");

            Console.WriteLine("Retrieving the change history.\n");
            // Retrieve the audit history for the account and display it.
            RetrieveRecordChangeHistoryRequest changeRequest = new RetrieveRecordChangeHistoryRequest();
            changeRequest.Target = new EntityReference(Contact.EntityLogicalName, entityId);

            RetrieveRecordChangeHistoryResponse changeResponse =
                (RetrieveRecordChangeHistoryResponse)XrmProxy.Execute(changeRequest);

            AuditDetailCollection details = changeResponse.AuditDetailCollection;

            foreach (AttributeAuditDetail detail in details.AuditDetails)
            {
                // Display some of the detail information in each audit record. 
                DisplayAuditDetails(detail);
            }
        }

DisplayAuditDetails (found in CRM SDK and modified a bit)

/// 
        /// Displays audit change history details on the console.
        /// 
        /// 
        private static void DisplayAuditDetails(AuditDetail detail)
        {
            // Write out some of the change history information in the audit record. 
            Entity record = detail.AuditRecord;

            Console.WriteLine("\nAudit record created on: {0}", record["createdon"]);
            Console.WriteLine("Entity: {0}, Action: {1}, Operation: {2}",
                record.LogicalName ,record.FormattedValues["action"],
                record.FormattedValues["operation"]);

            // Show additional details for certain AuditDetail sub-types.
            var detailType = detail.GetType();
            if (detailType == typeof(AttributeAuditDetail))
            {
                var attributeDetail = (AttributeAuditDetail)detail;

                // Display the old and new attribute values.
                foreach (KeyValuePair attribute in attributeDetail.NewValue.Attributes)
                {
                    String oldValue = "(no value)", newValue = "(no value)";

                    //TODO Display the lookup values of those attributes that do not contain strings.
                    if (attributeDetail.OldValue.Contains(attribute.Key))
                        oldValue = attributeDetail.OldValue[attribute.Key].ToString();

                    newValue = attributeDetail.NewValue[attribute.Key].ToString();

                    Console.WriteLine("Attribute: {0}, old value: {1}, new value: {2}",
                        attribute.Key, oldValue, newValue);
                }

                foreach (KeyValuePair attribute in attributeDetail.OldValue.Attributes)
                {
                    if (!attributeDetail.NewValue.Contains(attribute.Key))
                    {
                        String newValue = "(no value)";

                        //TODO Display the lookup values of those attributes that do not contain strings.
                        String oldValue = attributeDetail.OldValue[attribute.Key].ToString();

                        Console.WriteLine("Attribute: {0}, old value: {1}, new value: {2}",
                            attribute.Key, oldValue, newValue);
                    }
                }
            }
            Console.WriteLine();
        }

Result: