将enum类型的列添加到datatable列

Question

Given:

namespace VolumeProfileStateEntity
{
    public enum VolumeProfileState
    {
        AboveHigh,
        AboveValue,
        AtOrNearValue,
        BelowValue,
        BelowLow
    }
}

I want to add a column of type VolumeProfileState :

DataTable dt1 = new DataTable("State");

Adding columns to the DataTable is fine until I try to add a column of type VolumeProfileState :

// Add columns to the DataTable.
var dc1 = dt1.Columns.Add("TimeFrame",
            System.Type.GetType("System.String"));
dc1.ReadOnly = true;

dt1.Columns.Add("Hi",
         System.Type.GetType("System.Double"));
dt1.Columns.Add("Low",
        System.Type.GetType("System.Double"));
dt1.Columns.Add("Middle",
        System.Type.GetType("System.Double"));
dt1.Columns.Add("State",             
        System.Type.GetType("VolumeProfileStateEntity.VolumeProfileState"));

Exception thrown: 'System.ArgumentNullException' in System.Data.dll

I know I can make the column of type

System.Type.GetType("System.Int32")); 

but then I have problems when entering data because Int32 is not IConvertible to enum types AFAIK.

Am I doing something wrong, or is it only possible to add column types of System.X and not enums ?

Answer 1

you should use a database column as int, then cast the value to an enum when retrieving it. You could also do the column as a string then cast to an enum when retrieving it. but int storage is smaller.