/// <summary>
/// 向字段集添加或修改ObjectID和拥有指定几何类型与坐标系Shape字段，若字段存在且符合要求则不添加或修改
/// （ObjectID会在不同数据源中自动转换为OID/FID/OJBECTID）
/// </summary>
/// <param name="fields">字段集</param>
/// <param name="geometryType">需要添加的Shape字段存储的几何类型</param>
/// <param name="spatialRef">需要添加的Shape字段存储的坐标系</param>
/// <returns></returns>
public static IFields AddBaseFields(this IFields fields, esriGeometryType geometryType, ISpatialReference spatialRef)
{
IFieldsEdit fieldsEdit = (IFieldsEdit)fields;
var oidField = fields.GetFirstFieldsByType(esriFieldType.esriFieldTypeOID);
if (oidField == null)
{
fieldsEdit.AddField(CreateOidField());
}
var shapeField = fields.GetFirstFieldsByType(esriFieldType.esriFieldTypeGeometry);
if (shapeField == null)
{
fieldsEdit.AddField(CreateShapeField(geometryType, spatialRef));
}
else if (shapeField.GeometryDef.GeometryType != geometryType ||
shapeField.GeometryDef.SpatialReference != spatialRef)
{
IFieldEdit shapeFieldEdit = (IFieldEdit)shapeField;
shapeFieldEdit.GeometryDef_2 = CreateGeometryDef(geometryType, spatialRef);
}
return(fields);
}
/// <summary>
/// 从字段集中查找SHAPE字段，获取SHAPE字段包含的坐标系信息
/// </summary>
/// <param name="fields">字段集</param>
/// <returns></returns>
public static ISpatialReference GetSpatialRef(this IFields fields)
{
var shapeField = fields.GetFirstFieldsByType(esriFieldType.esriFieldTypeGeometry);
if (shapeField == null)
{
throw new Exception("字段集中不包含SHAPE字段！");
}
return(GetSpatialRef(shapeField));
}
/// <summary>
/// 创建要素类
/// </summary>
/// <param name="obj">IWorkspace、IFeatureWorkspace或IFeatureDataset对象，在该对象中创建要素类</param>
/// <param name="name">要素类名称（如果为shapefile,不能包含文件扩展名".shp"）</param>
/// <param name="fields">要创建的字段集（必须包含SHAPE字段），可参考<see cref="FieldOpt.CreateBaseFields"/>等方法创建字段集</param>
/// <returns></returns>
public static IFeatureClass Create(object obj, string name, IFields fields)
{
var shapeField = fields.GetFirstFieldsByType(esriFieldType.esriFieldTypeGeometry);
if (shapeField == null)
{
throw new Exception($"在要创建的字段集（参数{nameof(fields)}）中找不到几何字段，创建要素类时应指定几何字段以确定几何类型和坐标系！");
}
var geometryType = shapeField.GeometryDef.GeometryType; //几何类型
var spatialRef = shapeField.GetSpatialRef(); //坐标系
return(Create(obj, name, spatialRef, esriFeatureType.esriFTSimple, geometryType, fields, null, null, ""));
}