How to tell if a PropertyInfo is of a particular enum type?

Question

I have the following code:

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;
    }
}

When I get to a field of type Enum, or in this case NameSpace.MyEnum, I want to do something special. I can't simply SetValue because the value coming from the database is let's say "m" and the value in the Enum is "Mr". So I need to call another method. I know! Legacy systems right?

So how do I determine when a PropertyInfo item is of a particular enumeration type?

So in the above code I'd like to first check whether the PropertyInfo type is of a specif enum and if it is then call my method and if not then simply allow SetValue to run.

Instead of using Activator.CreateInstance(), just add the "new" constraint to your generic: "where T : class, new()". Then just use "T entity = new T()". That way, you can enforce the need for a parameterless constructor at compile time. — Brannon, Oct 09 '09 at 18:11
@Brannon, thanks that's a great tip. will do when i get into work. thanks. — griegs, Oct 10 '09 at 19:53

score 43 · Answer 1 · answered Oct 05 '11 at 02:58

43

Here is what I use with success

property.PropertyType.IsEnum

answered Oct 05 '11 at 02:58

Valamas

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2

While this doesn't answer the original question which is asking to identify an enum of a particular type, this is exactly what I was looking for. Many thanks. – Mark McGookin Aug 17 '20 at 07:42

score 4 · Answer 2 · answered Oct 08 '09 at 23:16

4

In your above code,

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

will get you whether or not the current type is (derived from) an enum or not.

answered Oct 08 '09 at 23:16

adrianbanks

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Matthew Whited · Accepted Answer · 2009-10-08T23:50:10.263

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; }
}

edited Oct 08 '09 at 23:50

answered Oct 08 '09 at 23:15

Matthew Whited

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It might be clearer just to test type == typeof(MyEnum). IsAssignableTo doesn't add any value because you can't have another type deriving from MyEnum. – itowlson Oct 08 '09 at 23:18
Thank you @Matthew. Works like a bought one. – griegs Oct 08 '09 at 23:27

score 0 · Answer 4 · answered Apr 27 '16 at 14:24

This is how I handle when I convert a data table into a strongly typed list

/// <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;
        }

How to tell if a PropertyInfo is of a particular enum type?

4 Answers4