Creating Feature Class in ArcObjects and C# says X Y domain on spatial reference system not set or invalid?

Question

I'm trying to create a Feature class. It shows the error

X Y domain on the spatial reference system is not set or in valid

Here is my code attempt:

      IWorkspaceFactory wsf = new  FileGDBWorkspaceFactory();
      IWorkspace ws = wsf.OpenFromFile(@"D:\ARC OBJECTS\Newgdb.gdb", 
                       ArcMap.Application.hWnd);
      IFeatureWorkspace fws = ws as IFeatureWorkspace;
      IFields flds = new FieldsClass();
      IFieldsEdit fldsedit = flds as IFieldsEdit;
      IField fld = new FieldClass();
      IFieldEdit fldedit = fld as IFieldEdit;
      fldedit.AliasName_2 = "Shape";
      fldedit.IsNullable_2 = false;
      fldedit.Name_2 = "Shape";
      fldedit.Type_2 = esriFieldType.esriFieldTypeGeometry;
      IGeometryDef gdef = new GeometryDefClass();
      IGeometryDefEdit gdedit = gdef as IGeometryDefEdit;
      gdedit.GeometryType_2 = esriGeometryType.esriGeometryPolygon;
      gdedit.SpatialReference_2 = new UnknownCoordinateSystemClass();
      fldedit.GeometryDef_2 = gdedit;
      fldsedit.AddField(fld);
      IFeatureClass feacls= fws.CreateFeatureClass("Error", flds, null,
                          null,esriFeatureType.esriFTSimple, "shape", "");

Where did I go wrong?

Answer 1

With a EPSG as parameter I work with this:

IGeometryDefEdit geometryDefEdit = new GeometryDefClass();
geometryDefEdit.GeometryType_2 = esriGeometryType.esriGeometryPoint;
ISpatialReferenceFactory spatialReferenceFactory = new SpatialReferenceEnvironmentClass();
ISpatialReference spatialReference = 
spatialReferenceFactory.CreateProjectedCoordinateSystem(EPSG); //or CreateGeographicCoordinateSystem
geometryDefEdit.SpatialReference_2 = spatialReference;

Then, when I define the field "Shape" I use:

IFieldsEdit fields = new FieldsClass();    
field = new FieldClass();
field.Name_2 = "Shape";
field.Type_2 = esriFieldType.esriFieldTypeGeometry;
field.GeometryDef_2 = geometryDefEdit as IGeometryDef;
fields.AddField(field);

Finally you have to add all the other fields...