Several questions about ESRI. ArcGIS. geoprocessor

1. Compiled with the ae9.2 + SP6 patchProgram
     Averagenearestneighbor avgnearneighbour = new averagenearestneighbor ();

     Avgnearneighbour. input_feature_class = inputstring;
    Input_feature_class: Input ifeaturelayer, whether it is a local shape file or SDE feature layer.

2. Under AE 9.3.1The input shape file can run normally, but the input SDE feature layer

    Igeoprocessorresult result = (igeoprocessorresult) GP. Execute (avgnearneighbour, null );

    Result is always null. I don't know why, so I have to use

    Database connections \ 10.1.161.84-CDC. Sde \ CDC. Public health \ CDC. Enterprises and institutions

    Such a string to solve

If anyone knows, please say thank you!