Сам же и нашел ответ на esri.com :)
может кому нибудь пригодиться:
using (WebMap webMap = Map1.CreateWebMap())
{
IServerContext serverContext;
IMapServer mapServer;
IMapDescription mapDesc;
serverContext = webMap.ServerContext;
mapServer = webMap.MapServer;
IMapServerObjects mapServerObj = (IMapServerObjects)mapServer;
string strMapName = mapServer.DefaultMapName;
IMap map = mapServerObj.get_Map(strMapName);
map.ClearLayers();
#region Set Server Properties
IPropertySet propertySet = serverContext.CreateObject("esriSystem.PropertySet") as IPropertySet;
propertySet.SetProperty("server", "linuxserver");
propertySet.SetProperty("instance", "esri_sde");
//propertySet.SetProperty("database", "HistMaps");
propertySet.SetProperty("user", "vovan");
propertySet.SetProperty("password", "vovan");
propertySet.SetProperty("version", "SDE.DEFAULT");
#endregion
IWorkspaceFactory workspaceFactory = serverContext.CreateObject("esriDataSourcesGDB.SdeWorkspaceFactory") as IWorkspaceFactory;
IWorkspace WS2 = workspaceFactory.Open(propertySet, 0) as IWorkspace;
IFeatureWorkspace featureWorkspace = workspaceFactory.Open(propertySet, 0) as IFeatureWorkspace;
IFeatureLayer l= null;
IFeatureClass fc = featureWorkspace.OpenFeatureClass(@LayerName);
IFeatureLayer fl = serverContext.CreateObject("esriCarto.FeatureLayer") as FeatureLayer;
fl.FeatureClass = fc;
fl.Name = fc.AliasName;
webMap.Map.AddLayer(fl);
map.get_Layer(0).Visible = true;
// Apply changes to MapServer object
mapServerObj.RefreshServerObjects();
webMap.Refresh();
}