public ESRI.ArcGIS.Geodatabase.IFeatureClass CreateFeatureClassForLine(ESRI.ArcGIS.Geodatabase.IWorkspace2 workspace, ESRI.ArcGIS.Geodatabase.IFeatureDataset featureDataset, System.String featureClassName)
        {
            ESRI.ArcGIS.esriSystem.UID CLSID = null;
            ESRI.ArcGIS.esriSystem.UID CLSEXT 
 
= null;
            System.String strConfigKeyword = null;
            if (featureClassName == "") returnnull; // name was not passed in 
            ESRI.ArcGIS.Geodatabase.IFeatureClass featureClass;
            ESRI.ArcGIS.Geodatabase.IFeatureWorkspace featureWorkspace = (ESRI.ArcGIS.Geodatabase.IFeatureWorkspace)workspace; 
 
// Explicit Castif (workspace.get_NameExists(ESRI.ArcGIS.Geodatabase.esriDatasetType.esriDTFeatureClass, featureClassName)) //feature class with that name already exists             {
                featureClass = featureWorkspace.OpenFeatureClass(featureClassName);
                return featureClass;
            }

            
 
// assign the class id value if not assignedif (CLSID == null)
            {
                CLSID = new ESRI.ArcGIS.esriSystem.UIDClass();
                CLSID.Value = "esriGeoDatabase.Feature";
                //CLSID.Value = "esriGeometryType.esriGeometryPolyline";            }

            ESRI.ArcGIS.Geodatabase.IObjectClassDescription objectClassDescription = new ESRI.ArcGIS.Geodatabase.FeatureClassDescriptionClass();
            ESRI.ArcGIS.Geodatabase.IFields fields = null;
            // if a fields collection is not passed in then supply our ownif (fields == null)
            {
                // create the fields using the required fields method
                fields = objectClassDescription.RequiredFields;
                ESRI.ArcGIS.Geodatabase.IFieldsEdit fieldsEdit = (ESRI.ArcGIS.Geodatabase.IFieldsEdit)fields; // Explicit Cast
                ESRI.ArcGIS.Geodatabase.IField field = new ESRI.ArcGIS.Geodatabase.FieldClass();

                // create a user defined text field
                ESRI.ArcGIS.Geodatabase.IFieldEdit fieldEdit = (ESRI.ArcGIS.Geodatabase.IFieldEdit)field; // Explicit Cast

                // setup field properties
                fieldEdit.Name_2 = "ZBDID";
                fieldEdit.Type_2 = ESRI.ArcGIS.Geodatabase.esriFieldType.esriFieldTypeString;
                fieldEdit.IsNullable_2 = true;
                fieldEdit.AliasName_2 = "座標編號";
                fieldEdit.DefaultValue_2 = "0";
                fieldEdit.Editable_2 = true;
                fieldEdit.Length_2 = 100;

                // add field to field collection                fieldsEdit.AddField(field);
                fields = (ESRI.ArcGIS.Geodatabase.IFields)fieldsEdit; // Explicit Cast            }

            System.String strShapeField = "";

            // locate the shape fieldfor (int j = 0; j < fields.FieldCount; j++)
            {
                if (fields.get_Field(j).Type == ESRI.ArcGIS.Geodatabase.esriFieldType.esriFieldTypeGeometry)
                {
                    //strShapeField = fields.get_Field(j).Name;
                    IField shapeField = fields.get_Field(j);
                    strShapeField = fields.get_Field(j).Name;
                    IGeometryDef geometryDef = shapeField.GeometryDef;
                    IGeometryDefEdit geometryDefEdit = (IGeometryDefEdit)geometryDef;

                    // Alter the feature class geometry type to lines (default is polygons).
                    geometryDefEdit.GeometryType_2 = esriGeometryType.esriGeometryPolyline;
                    geometryDefEdit.HasM_2 = true;//true 則帶有Z座標，false 不帶Z座標
                    geometryDefEdit.GridCount_2 = 1;

                    // Set the first grid size to zero and allow ArcGIS to determine a valid grid size.
                    geometryDefEdit.set_GridSize(0, 0);
                    ISpatialReferenceFactory3 spatialReferenceFactory = new SpatialReferenceEnvironmentClass();
                    geometryDefEdit.SpatialReference_2 = spatialReferenceFactory.CreateGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_Beijing1954);

                    break;
                }
            }

            // Use IFieldChecker to create a validated fields collection.
            ESRI.ArcGIS.Geodatabase.IFieldChecker fieldChecker = new ESRI.ArcGIS.Geodatabase.FieldCheckerClass();
            ESRI.ArcGIS.Geodatabase.IEnumFieldError enumFieldError = null;
            ESRI.ArcGIS.Geodatabase.IFields validatedFields = null;
            fieldChecker.ValidateWorkspace = (ESRI.ArcGIS.Geodatabase.IWorkspace)workspace;
            fieldChecker.Validate(fields, out enumFieldError, out validatedFields);

            // The enumFieldError enumerator can be inspected at this point to determine 
            // which fields were modified during validation.

            // finally create and return the feature classif (featureDataset == null)// if no feature dataset passed in, create at the workspace level            {
                featureClass = featureWorkspace.CreateFeatureClass(featureClassName, validatedFields, CLSID, CLSEXT, ESRI.ArcGIS.Geodatabase.esriFeatureType.esriFTSimple, strShapeField, strConfigKeyword);
            }
            else
            {
                featureClass = featureDataset.CreateFeatureClass(featureClassName, validatedFields, CLSID, CLSEXT, ESRI.ArcGIS.Geodatabase.esriFeatureType.esriFTSimple, strShapeField, strConfigKeyword);
            }
            return featureClass;
        }