CreateFeatureClass COM异常

private static IFeatureClass CreatStnShp(string shp)
{
//打开工作空间
IWorkspaceFactory wsfactory = new ShapefileWorkspaceFactoryClass();
string ssss = System.IO.Path.GetDirectoryName(shp);
IWorkspace workspace = wsfactory.OpenFromFile(ssss, 0);
IFeatureWorkspace pFeatWsp = workspace as IFeatureWorkspace;

if (File.Exists(shp))
{
DialogResult dr = MessageBox.Show("文件已经存在,是否使用该文件?", "提示",
MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
if ( dr== DialogResult.Yes)
{
return pFeatWsp.OpenFeatureClass(System.IO.Path.GetFileNameWithoutExtension(shp));
}
else if(dr==DialogResult.No)
{
//删除已有
DialogResult ddr = MessageBox.Show("是否删除并替换已有文件", "提示",
MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (ddr == DialogResult.Yes)
{
string dbffile = System.IO.Path.ChangeExtension(shp, ".dbf");
string shxfile = System.IO.Path.ChangeExtension(shp, ".shx");
string prjfile = System.IO.Path.ChangeExtension(shp, ".prj");
File.Delete(shp);
if (File.Exists(dbffile))
File.Delete(dbffile);
if (File.Exists(shxfile))
File.Delete(shxfile);
if (File.Exists(prjfile))
File.Delete(prjfile);
}
else
{
MessageBox.Show("请重新选择shapfile文件的路径");
}
}
else
{
return null;
}
}

IGeometryDefEdit pGeoDef = new GeometryDefClass();
pGeoDef.GeometryType_2 = esriGeometryType.esriGeometryPoint;

//设置空间参考
ISpatialReferenceFactory3 spatialReferenceFactory = new SpatialReferenceEnvironmentClass();
ISpatialReference pSr = spatialReferenceFactory.CreateGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_WGS1984);

//设置字段
IFieldEdit pField;
IFieldsEdit pFieldsEdit = new FieldsClass();
//设置几何字段
pField = new FieldClass();
pField.Type_2 = esriFieldType.esriFieldTypeGeometry;
pField.GeometryDef_2 = pGeoDef;
pField.Name_2 = "Shape";
pFieldsEdit.AddField(pField);
//产生唯一索引字段
pField = new FieldClass();
pField.Name_2 = "OBJECTID";
pField.Type_2 = esriFieldType.esriFieldTypeOID;
pFieldsEdit.AddField(pField);
//添加station相关字段
//string[] str = new string[]{"NCDCID","WBAN","NAME","COOPID","COUNTRY","STNTYPE"};
string[] str = new string[] { "WBAN", "NAME", "LOCATION", "LAT", "LON"};
foreach (string stt in str)
{
pField = new FieldClass();
pField.Name_2 = stt;
pField.AliasName_2 = stt;
pField.Type_2 = esriFieldType.esriFieldTypeString;
if (stt == "LOCATION")
pField.Length_2 = 60;
else
pField.Length_2 = 30;
pFieldsEdit.AddField(pField);
}
pField = new FieldClass();
pField.Name_2 = "StnHeight";
pField.Type_2 = esriFieldType.esriFieldTypeDouble;
pFieldsEdit.AddField(pField);

pField = new FieldClass();
pField.Name_2 = "GndHeight";
pField.Type_2 = esriFieldType.esriFieldTypeDouble;
pFieldsEdit.AddField(pField);

IFeatureClass pfeatcls =pFeatWsp.CreateFeatureClass(System.IO.Path.GetFileNameWithoutExtension(shp), pFieldsEdit as IFields, null, null,
esriFeatureType.esriFTSimple, "Shape", "");
IGeoDataset pGeoDs = pfeatcls as IGeoDataset;
IGeoDatasetSchemaEdit pGeoDSe = pGeoDs as IGeoDatasetSchemaEdit;
if (pGeoDSe.CanAlterSpatialReference)
{
pGeoDSe.AlterSpatialReference(pSr);
}

return pfeatcls;
}

上面是可正常运行的代码。自己写的时候凭着自己的理解做了部分修改，在字段声明的时候略有不同，如下

IFields pfs = new FieldsClass();
IFieldsEdit pFieldsEdit = pfs as IFieldsEdit;
IField pFieldd = new FieldClass();
IFieldEdit pField = pFieldd as IFieldEdit;

结果在运行的时候出现COM异常，仔细核查了CreateFeatureClass的每个参数，多次检查都没有查到结果。后来修改为文中第一段代码声明方式，再运行成功了。

为了找出错误，我又把声明换回第二段代码，令人郁闷的是，又没异常了。

本文只描述现象，不解释原因