How do you declare an ArcSDE workspace for a GP tool in 10.1 (c#)?

Question

What is the proper way to declare an SDE workspace for GP tools in c# .net?

I am using ArcGIS 10.1 SDE (MS SQL) on server 2008, i want to write code so that everynight the server will fire a program and compress one of my SDE databases. I thought i could do this in c# using the compress tool in the data management namespace but have run into a snag.

I am told my workspace is invalid. Esri help docs don't do me much good, as they just show generic help (http://resources.arcgis.com/en/help/arcobjects-net/componenthelp/#/in_workspace_Property/005400000202000000/) and my internet search has lead to bubkis. Can anyone tell me how to define a SDE workspace in 10.1 in net?

Right now i am using @"Database Connections\CME.sde" Here is the error:

Executing: Compress "Database Connections\CME.sde" Start Time: Fri Oct 12 13:40:47 2012 Failed to execute. Parameters are not valid. ERROR 000837: The workspace is not the correct workspace type. Failed to execute (Compress).

what should i be typing for the in_workspace?

private void button1_Click(object sender, EventArgs e)
        {

            Compress Compressor = new Compress();
            object in_workspace = @"Database Connections\CME.sde";




            Compressor.in_workspace = in_workspace;

            Geoprocessor GP = new Geoprocessor();
            RunTool(GP, Compressor, null);


        }
        private static void RunTool(Geoprocessor geoprocessor, IGPProcess process, ITrackCancel TC)
        {

            // Set the overwrite output option to true
            geoprocessor.OverwriteOutput = true;

            // Execute the tool            
            try
            {
                geoprocessor.Execute(process, null);
                ReturnMessages(geoprocessor);

            }
            catch (Exception err)
            {
                MessageBox.Show(err.Message); 
                ReturnMessages(geoprocessor);
            }
        }
        private static void ReturnMessages(Geoprocessor gp)
        {
            if (gp.MessageCount > 0)
            {
                for (int Count = 0; Count <= gp.MessageCount - 1; Count++)
                {
                  Console.WriteLine(gp.GetMessage(Count));

                }
            }

        }
    }

Answer 1

this code returns an SDE workspace, hopes can help

    // For example, connectionFile = @"C:\myData\Connection to Kona.sde".
    private static IWorkspace ArcSdeWorkspaceFromFile(String connectionFile)
    {
        Type factoryType = Type.GetTypeFromProgID(
            "esriDataSourcesGDB.SdeWorkspaceFactory");
        IWorkspaceFactory workspaceFactory = (IWorkspaceFactory)Activator.CreateInstance
            (factoryType);
        return workspaceFactory.OpenFromFile(connectionFile, 0);

    }