ics = new ClientServices2.ContentService.ContentServiceClient("WSHttpBinding_IContentService");

                ClientServices2.ContentService.FindContentParameters fcp = new ClientServices2.ContentService.FindContentParameters();

                fcp.SessionContext = sessionContext;
                fcp.ServiceID = TG4TestApp.Properties.Settings.Default.ServiceID;
                fcp.StartPos = startPos;
                fcp.MaxResult = maxResult;
                fcp.SortOption = sortOption;
//                fcp.PropertiesFilter = propertyFilter;
                //create PropertiesFilterParam placeholder %1.              
                ClientServices2.ContentService.PropertiesFilterParameter propParam = new ClientServices2.ContentService.PropertiesFilterParameter();
                propParam.PropertyName = "Date";              //name
                propParam.PropertyMatchString = "04/07/2011"; //value

                //create new PropertiesFilterParameters array and add the propParam
                fcp.PropertiesFilterParameters = new ClientServices2.ContentService.PropertiesFilterParameter[] { propParam };

                //set the property filter
                fcp.PropertiesFilter = "%1";               

                TG4TestApp.ClientServices2.ContentService.ContentVO[] cs = ics.FindContent(fcp);

Short example of how to use the FindCOntentParameters.PropertiesFilterParameters when searching andvanced properties (with special characters)

Advanced PropertiesFilterParameters

C#