Question

我有以下代码：

public class DataReader<T> where T : class
{
    public T getEntityFromReader(IDataReader reader, IDictionary<string, string> FieldMappings)
    {
        T entity = Activator.CreateInstance<T>();
        Type entityType = entity.GetType();
        PropertyInfo[] pi = entityType.GetProperties();
        string FieldName;

        while (reader.Read())
        {
            for (int t = 0; t < reader.FieldCount; t++)
            {
                foreach (PropertyInfo property in pi)
                {
                    FieldMappings.TryGetValue(property.Name, out FieldName);

                    Type genericType = property.PropertyType;

                    if (!String.IsNullOrEmpty(FieldName))
                        property.SetValue(entity, reader[FieldName], null);
                }
            }
        }

        return entity;
    }
}

当我到达Enum类型的字段，或者在这种情况下NameSpace.MyEnum时，我想做一些特别的事情。我不能简单地SetValue，因为来自数据库的值是“m”，而Enum中的值是“Mr”。所以我需要调用另一种方法。我知道！遗产系统对吗？

那么如何确定PropertyInfo项目何时具有特定的枚举类型？

因此，在上面的代码中，我想首先检查PropertyInfo类型是否具有特定的枚举，如果是，则调用我的方法，如果不是，则只需允许SetValue运行。

Answer 1

以下是我成功使用的内容

property.PropertyType.IsEnum

Answer 2

在上面的代码中，

bool isEnum = typeof(Enum).IsAssignableFrom(typeof(genericType));

无论当前类型是否（来自）枚举，

都会告诉您。

Answer 3

static void DoWork()
{
    var myclass = typeof(MyClass);
    var pi = myclass.GetProperty("Enum");
    var type = pi.PropertyType;

    /* as itowlson points out you could just do ...
        var isMyEnum = type == typeof(MyEnum) 
        ... becasue Enums can not be inherited
    */
    var isMyEnum = type.IsAssignableFrom(typeof(MyEnum)); // true
}
public enum MyEnum { A, B, C, D }
public class MyClass
{
    public MyEnum Enum { get; set; }
}

Answer 4

这是我将数据表转换为强类型列表时的处理方法

/// <summary>
        /// Covert a data table to an entity wiht properties name same as the repective column name
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dt"></param>
        /// <returns></returns>
        public static List<T> ConvertDataTable<T>(this DataTable dt)
        {
            List<T> models = new List<T>();
            foreach (DataRow dr in dt.Rows)
            {
                T model = (T)Activator.CreateInstance(typeof(T));
                PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));

                foreach (PropertyDescriptor prop in properties)
                {
                    //get the property information based on the type
                    System.Reflection.PropertyInfo propertyInfo = model.GetType().GetProperties().Last(p => p.Name == prop.Name);

                    var ca = propertyInfo.GetCustomAttribute<PropertyDbParameterAttribute>(inherit: false);
                    string PropertyName = string.Empty;
                    if (ca != null && !String.IsNullOrWhiteSpace(ca.name) && dt.Columns.Contains(ca.name))  //Here giving more priority to explicit value
                        PropertyName = ca.name;
                    else if (dt.Columns.Contains(prop.Name))
                        PropertyName = prop.Name;

                    if (!String.IsNullOrWhiteSpace(PropertyName))
                    {
                        //Convert.ChangeType does not handle conversion to nullable types
                        //if the property type is nullable, we need to get the underlying type of the property
                        var targetType = IsNullableType(propertyInfo.PropertyType) ? Nullable.GetUnderlyingType(propertyInfo.PropertyType) : propertyInfo.PropertyType;
                        // var propertyVal = Convert.ChangeType(dr[prop.Name], targetType);
                        //Set the value of the property
                        try
                        {
                            if (propertyInfo.PropertyType.IsEnum)
                                prop.SetValue(model, dr[PropertyName] is DBNull ? (object)null : Enum.Parse(targetType, Convert.ToString(dr[PropertyName])));
                            else
                                prop.SetValue(model, dr[PropertyName] is DBNull ? (object)null : Convert.ChangeType(dr[PropertyName], targetType));
                        }
                        catch (Exception ex)
                        {
                            //Logging.CustomLogging(loggingAreasType: LoggingAreasType.Class, loggingType: LoggingType.Error, className: CurrentClassName, methodName: MethodBase.GetCurrentMethod().Name, stackTrace: "There's some problem in converting model property name: " + PropertyName + ", model property type: " + targetType.ToString() + ", data row value: " + (dr[PropertyName] is DBNull ? string.Empty : Convert.ToString(dr[PropertyName])) + " | " + ex.StackTrace);
                            throw;
                        }
                    }
                }
                models.Add(model);
            }
            return models;
        }

如何判断PropertyInfo是否属于特定的枚举类型？

4 个答案: