Geoprocessing JoinField C# Usage Error

Question

I'm trying to join a single column from one feature class to another inside a File GDB using C# and the ESRI.ArcGIS.DataManagementTools.JoinField class. I've gotten several other geoprocessing functions to work, but for this one I don't think I have the correct input to the 'fields' property to specify the column to be joined and the gp.Execute() throws a COM exception. I've tried an IFields object (in the code below), I've tried a simple text string with the name of the field. They both throw a COM exception with no useful information.

    IFeatureClass parcelsExportFC = exportFws.OpenFeatureClass(parcelsExportFClassName);
    IFeatureClass parcelsZoneJoin = exportFws.OpenFeatureClass(String.Format("{0}_ZONEJOIN", parcelsExportFClassName));
    Int32 parcelsExportOIDFieldIdx = parcelsExportFC.Fields.FindField("OBJECTID");
    Int32 parcelsZoneJoinOrig_OIDFieldIdx = parcelsZoneJoin.Fields.FindField("ORIG_OID");
    IField parcelsExportOIDField = parcelsExportFC.Fields.get_Field(parcelsExportOIDFieldIdx);
    IField parcelsZoneJoinOrig_OIDField = parcelsZoneJoin.Fields.get_Field(parcelsZoneJoinOrig_OIDFieldIdx);
    JoinField jf = new JoinField(parcelsExportFC, parcelsExportOIDField, parcelsZoneJoin, parcelsZoneJoinOrig_OIDField);
    //this is the field I want to join
    IField zoneCodeField = parcelsZoneJoin.Fields.get_Field(parcelsZoneJoin.FindField("ZONE"));
    IFieldsEdit fields = new FieldsClass();
    fields.FieldCount_2 = 1;
    fields.set_Field(0, zoneCodeField);
    jf.fields = (IFields)fields;
    Geoprocessor gp = new Geoprocessor();
    gp.Execute(jf, null);

Any ideas?

Answer 1

So I had some JoinField parameters ordered wrong, and it works if you specify a text field like so:

    jf.fields = "AvistaCode";

Not sure how you would specify multiple fields though.