请教ArcGIS添加字段问题

Question

我写了添加字段的代码， public static void AddField_IClass(IFeatureClass featureClass, string fieldName, string aliasName,
esriFieldType type, int fieldLen, int precision, bool allowNull)
{
if (featureClass == null || fieldName == null || fieldName.Trim() == "")
return;

        IFields pFields = featureClass.Fields;
        if (pFields.FindField(fieldName) >= 0)
            return;
        IClass pClass = featureClass as IClass;
        IFieldsEdit pFieldsEdit = pFields as IFieldsEdit;
        IField pField = new FieldClass();
        IFieldEdit pFieldEdit = pField as IFieldEdit;
        try
        {
            addFiled(ref pFieldEdit, fieldName, aliasName, type, fieldLen, precision, allowNull);
                            /***********出错位置****************/
            pClass.AddField(pField);
        }
        catch (Exception e)
        {
            throw e;
        }
    }

    private static void addFiled(ref IFieldEdit fieldEdit, string fieldName, string aliasName, esriFieldType type, int fieldLen, int precision, bool allowNull)
    {
        try
        {
            fieldEdit.Name_2 = fieldName;
            if (aliasName != null && aliasName.Trim() != "")
                fieldEdit.AliasName_2 = aliasName;
            fieldEdit.Type_2 = type;
            fieldEdit.Length_2 = fieldLen;
            if (type == esriFieldType.esriFieldTypeDouble || type == esriFieldType.esriFieldTypeSingle)
            {
                fieldEdit.Precision_2 = precision;//小数位数
            }
            fieldEdit.IsNullable_2 = allowNull;
        }
        catch (Exception e)
        {
            throw e;
        }
    }
            请教一下，我批量为图层创建字段，同样的字段在有些图层中能创建成功，有些就会把错，这是为什么呢？我跟踪看了一下，每个变量的值都存在。

Answer 1

打开catalog，找到相应的层，右键-属性，在fields选项中增加或者删除字段，但不能修改